Atlantica Sustainable Infrastructure plc, or the Company, we or us, may from time to time, in one or more offerings, offer and sell ordinary shares, senior or subordinated debt securities or warrants. Each time we sell any of the securities described in this prospectus, we will provide one or more supplements to this prospectus that will contain specific information about those securities and their offering. Specific amounts and terms of any such securities will be provided in such supplements to this prospectus. You should read this prospectus and any prospectus supplement(s) carefully before you invest.

Our ordinary shares are listed on the NASDAQ Global Select Market under the symbol “AY.” We have not yet determined whether any other securities that may be offered by this prospectus may be listed on any exchange, interdealer quotation system or over-the-counter market. If we decide to seek the listing of any such securities upon issuance, the prospectus supplement relating to those securities will disclose the exchange, interdealer quotation system or over-the-counter market on which the securities will be listed.

We may offer and sell the securities covered by this prospectus to or through one or more underwriters, dealers and agents, or directly to investors, in amounts, at prices and on terms to be determined by market conditions and other factors at the time of the offering. This prospectus describes only the general terms that may apply to the securities covered by this prospectus and the general manner in which we may offer to sell such securities. The specific terms of any securities to be offered, and the specific manner in which they may be offered, will be described in one or more supplements to this prospectus. Any prospectus supplement may also add, update or change information contained in this prospectus.

You should carefully read this prospectus and any accompanying prospectus supplement, together with the documents we incorporate by reference, before you invest in our ordinary shares, senior or subordinated debt securities or warrants. We also encourage you to read the documents we have referred you to in the “Where You Can Find More Information” section of this prospectus for information on us and for our financial statements.

Investing in the securities covered by this prospectus involves certain risks. You should carefully consider the risks identified in “Risk Factors” beginning on page 8 of this prospectus, in the “Risk Factors” section of our most recent Annual Report on Form 20-F and in any applicable prospectus supplement or other offering materials before making your investment decision.

Neither the Securities and Exchange Commission nor any state securities commission or any other regulatory body has approved or disapproved of these securities or determined if this prospectus is truthful or complete. Any representation to the contrary is a criminal offense.

This prospectus is part of a registration statement on Form F-3 that we filed with the Securities and Exchange Commission (the “Registration Statement”), or the SEC, on the date hereof utilizing a shelf registration process. Under this shelf registration process, we may, from time to time, offer and sell any combination of the securities described in this prospectus in one or more offerings.

This prospectus provides you with a general description of the securities we may offer. Each time we offer and sell any of the securities covered by this prospectus, we will provide a prospectus supplement along with this prospectus that will contain specific information about the terms of that particular offering by us. The accompanying prospectus supplement may also add, update or change information contained in this prospectus. If there is any inconsistency between the information contained in this prospectus and any prospectus supplement, you should rely on the information contained in such prospectus supplement.

You should read both this prospectus and the accompanying prospectus supplement together with the additional information described under the heading “Where You Can Find More Information” before purchasing any of our securities. You should also carefully consider, among other things, the matters identified in “Risk Factors” beginning on page 8 of this prospectus and in our most recent Annual Report on Form 20-F before making your investment decision.

The prospectus supplement to be attached to the front of this prospectus will describe, among other matters, the terms of the offering, including the amount and detailed terms of the securities, the public offering price, net proceeds to us, the expenses of the offering, our capitalization, the nature of the plan of distribution, the other specific terms related to such offering and any material United Kingdom and United States federal income tax considerations applicable to the securities being offered.

In this prospectus, (i) “Atlantica,” the “Company,” “we,” “us,” “our” and “our Company” refers to Atlantica Sustainable Infrastructure plc and, where the context requires, its direct and indirect subsidiaries, (ii) “Abengoa” refers to Abengoa, S.A., together with its subsidiaries, (iii) “Adjusted EBITDA” refers to the meaning set forth in “Presentation of Financial Information—Non-GAAP Financial Measures” in our most recent Annual Report on Form 20-F, (iv) “Algonquin” refers to Algonquin Power & Utilities Corp., together with its subsidiaries, (v) “Pemex” refer to Petróleos Mexicanos and (vi) “PG&E” refers to PG&E Corporation and its regulated utility subsidiary, Pacific Gas and Electric Company collectively.

You should rely only on the information contained or incorporated by reference in this prospectus and any accompanying prospectus supplement. We have not authorized anyone to provide you with additional or different information. If any person provides you with different or inconsistent information, you should not rely on it. We are not making an offer of securities in any jurisdiction where an offer or sale is not permitted. You should not assume that the information in this prospectus or any prospectus supplement, as well as the information we previously filed with the SEC that we incorporate by reference in this prospectus or any prospectus supplement, is accurate as of any date other than its respective stated date. Our business, financial condition, results of operations and prospects may have changed since that date. Information contained on our website does not constitute part of this prospectus.

Atlantica is a public limited company organized under the laws of England and Wales. A majority of our directors and officers and certain other persons named in this prospectus reside outside the United States and all or a significant portion of the assets of the directors and officers and certain other persons named in this prospectus and a significant portion of our assets are located outside the United States. As a result, it may be difficult or impossible for investors to effect service of process within the United States upon us or such persons with respect to matters arising under U.S. federal securities law or to enforce against us or such persons judgments of the courts of United States predicated upon civil liability provisions under U.S. federal securities law.

We have appointed Atlantica North America LLC as our agent upon whom process may be served in any action brought against us under the laws of the United States. We have been advised that there is doubt as to the enforceability in England and Wales, in original actions or in actions for enforcement of judgments of U.S. courts, of civil liability based solely on the U.S. federal securities laws.

This prospectus, which forms part of the registration statement on Form F-3 we filed with the SEC under the Securities Act, does not contain all the information set forth in the registration statement and the exhibits and schedules to the registration statement. For further information, we refer you to the registration statement and the exhibits and schedules filed as part of the registration statement. The registration statement contains more information than this prospectus regarding us and our ordinary shares, including certain exhibits and schedules. With respect to the statements contained in this prospectus supplement and the accompanying prospectus regarding the contents of any agreement or any other document, in each instance, the statement is qualified in all respects by the complete text of the agreement or document, a copy of which has been filed as an exhibit to the registration statement. You can obtain a copy of the registration statement from the SEC’s website. The SEC maintains a website that contains reports, proxy and information statements and other information regarding registrants that file electronically through the SEC’s Electronic Data Gathering, Analysis and Retrieval system, or EDGAR, including the Company, which can be accessed at http://www.sec.gov.

We file annual and other reports with the SEC. We are subject to those reporting requirements of the Securities Exchange Act of 1934, or the Exchange Act, that are applicable to a foreign private issuer. In accordance with the Exchange Act, we file reports with the SEC, including annual reports on Form 20-F. We also furnish to the SEC, under cover of Form 6-K, material information that we are required or choose to make public or that we distribute, or that is required to be distributed by us, to our shareholders.

We maintain a corporate website at www.atlantica.com. Information contained on, or that can be accessed through, our website does not constitute a part of this Registration Statement. We have included our website address in this prospectus solely as an inactive textual reference.

As a foreign private issuer, we are exempt under the Exchange Act from, among other things, the rules prescribing the furnishing and content of proxy statements, and our executive officers, directors and principal shareholders are exempt from the reporting and short-swing profit recovery provisions contained in Section 16 of the Exchange Act. In addition, we are required under the Exchange Act to file periodic reports and financial statements with the SEC as frequently or as promptly as U.S. companies whose securities are registered under the Exchange Act.

The SEC allows us to “incorporate by reference” into this prospectus certain information we file with the SEC. This means that we can disclose important information to you by referring you to another document filed separately with the SEC. Each document incorporated by reference is current only as of the date of such document, and the incorporation by reference of such documents shall not create any implication that there has been no change in our affairs since the date thereof or that the information contained therein is current as of any time subsequent to its date. The information incorporated by reference is considered to be a part of this prospectus and should be read with the same degree of care. When we update the information contained in documents that have been incorporated by reference by making future filings with the SEC, the information incorporated by reference in this prospectus is considered to be automatically updated and superseded. In the case of a conflict or inconsistency between information contained in this prospectus and information incorporated by reference into this prospectus, you should rely on the information contained in the document that was filed later.

This prospectus incorporates by reference the following documents:

These reports contain important information about us, our financial condition and our results of operations.

All Annual Reports on Form 20-F, and any Reports of Foreign Private Issuer on Form 6-K which are identified by us as being incorporated by reference (to the extent designated therein), filed with or submitted to the SEC subsequent to the date of this prospectus, but before termination of the offering under this prospectus, shall be deemed incorporated by reference into this prospectus and deemed to be a part hereof from the date of the filing of such documents. Unless expressly incorporated by reference, nothing in this prospectus shall be deemed to incorporate by reference information furnished to, but not filed with, the SEC. Documents incorporated by reference are available from us, without charge, by writing to or calling:

This prospectus and any prospectus supplement and the documents we incorporate by reference include forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995. Any statements that express, or involve discussions as to, expectations, beliefs, plans, objectives, assumptions, strategies, future events or performance (often, but not always, through the use of words or phrases such as may result, are expected to, will continue, is anticipated, believe, will, could, should, would, estimated, may, plan, potential, future, projection, goals, target, outlook, predict and intend or words of similar meaning) are not statements of historical facts and may be forward looking. Such statements occur throughout this prospectus and include statements with respect to our expected trends and outlook, potential market and currency fluctuations, occurrence and effects of certain trigger and conversion events, our capital requirements, changes in market price of our shares, future regulatory requirements, the ability to identify and/or consummate future investments and acquisitions on favorable terms, reputational risks, divergence of interests between our company and that of our largest shareholder, tax and insurance implications, and more. Forward-looking statements involve estimates, assumptions and uncertainties. Accordingly, any such statements are qualified in their entirety by reference to, and are accompanied by, important factors included in the section “Risk Factors” herein, the "Risk Factors" section of our most recent Annual Report on Form 20-F, any prospectus supplement and any other document that is, or may be, filed with the SEC that is incorporated by reference herein (in addition to any assumptions and other factors referred to specifically in connection with such forward-looking statements) that could have a significant impact on our operations and financial results, and could cause our actual results to differ materially from those contained or implied in forward-looking statements made by us or on our behalf in this prospectus, in presentations, on our website, in response to questions or otherwise. These forward-looking statements include, but are not limited to, statements relating to:

Any forward-looking statement made in this prospectus or any prospectus supplement, or any information incorporated by reference herein or therein speaks only as of the date on which such statement is made, and we undertake no obligation to update any forward-looking statement to reflect events or circumstances, including, but not limited to, unanticipated events, after the date on which such statement is made, unless otherwise required by law. New factors emerge from time to time and it is not possible for management to predict all of such factors, nor can it assess the impact of each such factor on the business or the extent to which any factor, or combination of factors, may cause actual results to differ materially from those contained or implied in any forward-looking statement.

An investment in securities involves a high degree of risk. Before you invest in securities issued by us, you should carefully consider the risks involved. Accordingly, you should carefully consider:

The discussion of risks related to our business contained in or incorporated by reference into this prospectus or into any prospectus supplement comprises material risks of which we are aware. If any of the events or developments described actually occur, our business, financial condition or results of operations would likely suffer. You should consider carefully the risk factors identified above and in any report on Form 6-K filed subsequent hereto to the extent that the forms we file expressly state that we incorporate them (or such portions) by reference in this prospectus, as well as other information in or incorporated by reference in this prospectus and any prospectus supplement, before purchasing any of our securities.

Unless the applicable prospectus supplement otherwise indicates, the net proceeds from the sale of securities offered by the Company pursuant to this prospectus will be used for general corporate purposes. General corporate purposes may include acquisitions, retirement of debt, investment in our subsidiaries, working capital and other business purposes.

The following description of our share capital is a summary of the material terms of our articles of association (the “Articles”) and applicable provisions of law. We have summarized certain portions of the Articles below. The Articles are incorporated by reference as an exhibit to the Registration Statement of which this prospectus forms a part. You should read the Articles for the provisions that are important to you.

Our share capital is $11,083,320.4 divided into approximately 110,833,204 ordinary shares, completely subscribed and disbursed and having a nominal value of $0.10 per share, all in the same class and series.

On June 18, 2014, Atlantica closed its initial public offering issuing 24,850,000 ordinary shares. The shares were sold at a price of $29 per share and as a result the Company raised $720,650,000 of gross proceeds. The Company recorded $2,485,000 as Share Capital and $682,810,000 as Additional Paid in Capital, included in Atlantica reserves as of December 31, 2016, corresponding to the total net proceeds of the offering. The underwriters further purchased 3,727,500 additional shares from the selling shareholder, a subsidiary wholly owned by Abengoa, at the public offering price less fees and commissions to cover over-allotments driving the total proceeds of the offering to $828,748,000. Atlantica’s shares began trading on the NASDAQ Global Select Market under the symbol “ABY” on June 13, 2014. The symbol changed to “AY” on November 11, 2017. On January 22, 2015, Abengoa closed an underwritten public offering and sale in the United States of 10,580,000 of ordinary shares of the Company for total proceeds of $327,980,000 (or $31 per share). As a result of such offering, Abengoa reduced its stake in the Company from 64.3% to 51.1% of its shares. On May 14, 2015 Atlantica issued 20,217,260 new shares at $33.14 per share, which was based on a 3% discount versus the May 7, 2015 closing price. Abengoa subscribed for 51% of the newly-issued shares and maintained its previous stake in Atlantica. The proceeds were primarily used by Atlantica to finance asset acquisitions in May and June 2015. On July 14, 2015, Abengoa sold 2,000,000 shares of Atlantica under Rule 144, reducing its stake to 49.1%. On March 5, 2015, Abengoa sold an aggregate of $279 million of principal amount of exchangeable notes due 2017, or the 2017 Exchangeable Notes. The 2017 Exchangeable Notes were exchangeable, at the option of their holders, for ordinary shares of Atlantica. As of September 23, 2016, according to publicly available information, Abengoa had delivered an aggregate of 7,595,639 shares of the Company to holders that exercised their option to exchange the 2017 Exchangeable Notes. As a result, Abengoa held 41.47% of our ordinary shares as of that date. On November 1, 2017, Algonquin entered into an agreement to purchase 25,054,315 shares from Abengoa, which closed on March 9, 2018. On April 17, 2018, Algonquin acquired the remaining 16.47% equity interest in the Company. On May 17, 2019, we issued 1,384,402 new shares, which were fully subscribed and paid up by Algonquin. On July 17, 2020 (and subsequently on July 29, 2020 pursuant to an over-allotment option), Atlantica issued an aggregate of $115 million of principal amount of exchangeable notes due 2025, or the 2025 Exchangeable Notes. The 2025 Exchangeable Notes are exchangeable, at the option of their holders during prescribed periods or upon the occurrence of specified corporate events, for our ordinary shares at an initial exchange rate of 29.1070 ordinary shares per $1,000 principal amount of notes (subject to adjustment). Based on such initial exchange rate, Atlantica would be required to issue up to 3,347,305 new ordinary shares in connection with the exchange of the 2025 Exchangeable Notes. On December 11, 2020, Atlantica issued 5,069,200 ordinary shares in an underwritten public offering at a price of $33 per new share. On January 7, 2021, Algonquin subscribed 4,020,860 ordinary shares of Atlantica pursuant to a private placement at a price of $33 per new share. Under our Long Term Incentive Plan, under which we grant awards as restricted stock units subject to certain vesting conditions, we issued 106,016 new shares in the first quarter of 2021 and 35,466 new shares in the second quarter of 2021.

None.

We are not permitted under English law to hold our own shares unless they are repurchased by us and held in treasury.

The following table presents the history of our share capital as of the end of each of our last three fiscal years:

We were incorporated in England and Wales on December 17, 2013, registered number 08818211. The Companies Act abolishes the need for an objects clause and, as such, our objects are unrestricted.

The Companies Act requires that an office holder disclose to the Company any personal interest that he or she may have, and all related material information and documents known to him or her, in connection with any existing or proposed transaction by the Company. The disclosure is required to be made promptly and in any event, no later than at the board of directors meeting in which the transaction is first discussed.

Subject to the provisions of the Articles, the directors may meet for the dispatch of business and adjourn and otherwise regulate its proceedings as they think fit. Unless and until in a general meeting the shareholders of the Company determine otherwise, the number of directors of the Company shall not be less than 7 nor more than 13 in number.

The quorum necessary for the transaction of business of the directors may be fixed from time to time by the directors and unless so fixed at any other number shall be a number equal to at least half of the directors appointed from time to time. A meeting of the directors at which a quorum is present shall be competent to exercise all powers and discretions for the time being exercisable by the directors. A director is not counted in the quorum at a meeting in relation to any resolution on which he or she is debarred from voting.

Subject to the provisions of the Companies Act, a director is entitled to vote and be counted in the quorum in respect of any resolution concerning any contract, transaction or arrangement or any other proposal (inter alia):

Any director (including the director that has the conflict) may propose that such conflicted director be authorized in relation to any matter which is the subject of such a conflict. The director with the conflict will not count towards the quorum at the meeting at which the conflict is considered and may not vote on any resolution authorizing the conflict. Where the board of directors gives authority in relation to such a conflict, the board of directors may impose such terms on the relevant director as it deems appropriate.

Each of our directors and other officers may be indemnified by us against all costs, charges, losses, expenses and liabilities incurred by such director or officer in the execution or discharge of his or her duties or in relation to those duties. The Companies Act renders void an indemnity for a director against any liability attaching to him or her in connection with any negligence, default, breach of duty or breach of trust in relation to the company of which he or she is a director. We have insurance for our directors regarding negligence, default, breach of trust and breach of duty under the terms allowed under the Companies Act.

The Companies Act requires that a resolution approving provisions to appoint a director for a period of more than two years must not be passed unless a memorandum setting out the proposed contract incorporating the provision is made available to members: in the case of a resolution at a meeting, by being made available for inspection by members of the company both (i) at the company’s registered office for not less than 15 days ending with the date of the meeting, and (ii) at the meeting itself.

Subject to certain minimum thresholds in terms of their shareholdings, each shareholder shall be entitled to appoint a number of directors in proportion to their shareholding. However, no shareholder shall be entitled to appoint more than half of the directors plus one.

Effective from October 1, 2013, quoted companies must obtain a binding vote of shareholders on remuneration policy at least once every three years and an advisory vote on an implementation report on how the remuneration policy was implemented in the relevant financial year.

The ordinary remuneration of the directors shall be determined by the directors.

Any director who holds any other office in our Company (including for this purpose the office of chairman or deputy chairman, whether or not such office is held in an executive capacity), or who serves on any committee of the directors, or who otherwise performs, or undertakes to perform, services which in the opinion of the directors are outside the scope of the ordinary duties of a director, may be paid such additional remuneration (whether by way of fixed sum, bonus commission, participation in profits or otherwise) or may receive such other benefits as the directors may determine.

Subject to the provisions of the Articles and the Companies Act, the directors may exercise all the powers of the Company to borrow money, mortgage or charge all or any part or parts of its undertaking, property and uncalled capital, and issue debentures and other securities whether outright or as collateral security for any debt, liability or obligation of the Company or of any third party.

The Company may, by ordinary resolution of which special notice has been given, remove any director and elect another person in place of such director.

Pursuant to the Articles, each director shall retire at the annual general meeting held in the third calendar year following the year in which he was elected or last re-elected by the Company or such shorter period as the directors may determine. In addition, each director (other than the Chairman and any director holding an executive office) shall also be required to retire at each annual general meeting following the ninth anniversary on the date on which he was elected by the Company. However, the Company’s board of directors resolved on November 4, 2020 that, commencing with the Company’s annual general meeting in 2021, each director will be submitted for re-election at each annual general meeting of the Company.

A director who retires at any annual general meeting shall be eligible for election or re- election unless the directors resolve otherwise not later than the date of the notice of such annual general meeting.

When a director retires at an annual general meeting in accordance with the Articles, the Company may, by ordinary resolution at the meeting, fill the office being vacated by re-electing the retiring director. In the absence of such a resolution, the retiring director shall nevertheless be deemed to have been re-elected, except in the cases identified by the Articles.

The office of a director of the Company shall be terminated if:

A director shall not be required to hold any shares of the Company by way of qualification. A director who is not a member of the Company shall nevertheless be entitled to attend and speak at general meetings.

On February 26, 2021, the Board approved a share ownership requirement applicable to directors receiving remuneration from the Company and executives (see “Item 6. Directors, Senior Management and Employees – E. Share Ownership” in our most recent Annual Report on Form 20-F). Within a period of five years, directors receiving remuneration from the Company should have a minimum share ownership in the Company of 3 times their annual compensation. In the case of the CEO, this requirement is 6 times his fixed compensation.

As of December 31, 2020, our shares have attached to them full voting, dividend and capital distribution (including winding up) rights. However, our shares do not confer any rights of redemption.

Without prejudice to any rights attached to any existing shares, the Company may issue shares with such rights or restrictions as determined either by the Company by ordinary resolution or, if the Company passes a resolution to authorize them, the directors. The Company may also issue shares which are, or are liable to be, redeemed at the option of the Company or the holder.

Dividend Rights. Our Articles provide that the Company may, by ordinary resolution, declare final dividends to be paid to its shareholders in accordance with their respective rights. However, no dividend shall be declared unless it has been recommended by the directors and does not exceed the amount recommended by the directors.

If the directors believe that the profits of the Company justify such payment, they may pay fixed dividends on any class of shares where the fixed dividend is payable on fixed dates. They may also pay interim dividends on shares of any class in amounts and on dates and periods as they think fit. Provided the directors act in good faith, they shall not incur any liability to the holders of any shares for any loss they may suffer by the lawful payment of dividends on any other class of shares having rights ranking equally with or behind those shares.

Unless the share rights otherwise provide, all dividends shall be declared and paid according to the amounts paid up on the shares on which the dividend is paid, and apportioned and paid pro rata according to the amounts paid on the shares during any portion or portions of the period in respect of which the dividend is paid.

Any unclaimed dividends may be invested or otherwise applied for the benefit of the Company until they are claimed. If any dividend is unclaimed for 12 years from the date on which it was declared or became due for payment, the person who was otherwise entitled to it shall cease to be entitled and the Company may keep that sum. In addition, the Company will not be considered a trustee with respect to the amount of any payment into a separate account by the directors of any unclaimed dividend or other sum payable on or in respect of a share of the Company.

The Company may cease to send any check or other means of payment by post for any dividend on any shares which is normally paid in that manner if in respect of at least two consecutive dividends payable on those shares, the check, warrant or order has been returned undelivered or remains uncashed but, subject to the provisions of these Articles, shall recommence sending checks, warrants or orders in respect of the dividends payable on those shares if the holder of or person entitled to them claims the arrears of dividend and does not instruct the Company to pay future dividends in some other way.

The directors may, if authorized by ordinary resolution, offer to shareholders the right to elect to receive, in lieu of a dividend, an allotment of new shares credited as fully paid.

Voting Rights. Subject to the provisions in the Articles and any special rights or restrictions as to voting attached to any shares or class of shares of the Company, at a general meeting, voting on each and every resolution shall be taken by way of a poll.

As such, every member present in person or by proxy has one vote for every share held by him or her, as per the Articles.

A proxy shall not be entitled to vote where the member appointing the proxy would not have been entitled to vote on the resolution had he been present in person.

In the case of joint holders of a share, the vote of the senior who tenders a vote, whether in person or by proxy, shall be accepted to the exclusion of the votes of the other joint holders and for this purpose seniority shall be determined by the order in which the names appear in the register of the Company in respect of the joint holding.

The actions necessary to change the rights of holders of the shares are as follows pursuant to the Companies Act: the rights of the shareholders would need to be altered by way of a special resolution requiring 75% vote of the shareholders who are present and voting in person or by proxy. In order to change the rights of a separate class of shares, it will require such a vote by shareholders of that class of shares.

Liquidation Rights. In the event of our liquidation, subject to applicable law, after satisfaction of liabilities to creditors, our assets will be distributed to the holders of shares in proportion to their respective holdings. This liquidation right may be affected by the grant of preferential dividends or distribution rights to the holders of a class of shares with preferential rights that may be authorized in the future.

Redemption Provisions. We may, subject to applicable law and to our Articles, issue redeemable preference shares and redeem the same.

Capital Calls. Under our Articles and the Companies Act, the liability of our shareholders is limited to the amount (if any) for the time being unpaid on the shares held by that member.

Subject to the terms of allotment of the shares of the Company, the directors of the Company may make a call on our shareholders to pay up any nominal value or share premium outstanding by giving them notices of such call. A shareholder must pay to the Company the amount called on his or her shares but is not required to do so until 14 days have passed since the notice of call was sent. If a shareholder fails to pay any part of a call, the directors may serve further notice naming another day not being less than seven days from the date of the further notice requiring payment and stating that in the event of non-payment the shares on which the call has been made will be liable to be forfeited. Subsequent forfeiture requires a resolution by the directors. As part of the initial public offering, the nominal value and share premium of all shares will be fully paid.

Transfer of Shares. Fully-paid shares are issued in registered form and may be transferred pursuant to our Articles, unless such transfer is restricted or prohibited by another instrument and subject to applicable securities laws.

Transfers of uncertificated shares may be effected by means of a relevant system (i.e., NASDAQ Global Select Market) unless the UK Uncertificated Securities Regulations 2001 (also known as the CREST Regulations) provide otherwise.

Preemptive Rights. In certain circumstances, our shareholders have preemptive rights under the Companies Act with respect to new issuances of equity securities.

Whenever the share capital of the Company is divided into different classes of shares, the special rights attached to any class may be varied or abrogated either with the written consent of the holders of three-quarters in nominal value of the issued shares of the class (excluding shares held as treasury shares) or with the sanction of a special resolution passed at a separate meeting of the holders of the shares of the class (but not otherwise), and may be so varied or abrogated either while the Company is a going concern or during or in contemplation of a winding-up.

The special rights attached to any class of shares will not, unless otherwise expressly provided by the terms of issue, be deemed to be varied by (i) the creation or issue of further shares ranking, as regards participation in the profits or assets of the Company, in some or all respects equally with them but in no respect in priority to them, or (ii) the purchase or redemption by the Company of any of its own shares.

An annual general meeting shall be held in each period of six months beginning with the day following the Company’s accounting reference date, at such place or places, date and time as may be decided by the directors.

The directors may, whenever they think fit, call a general meeting. The directors are required to call a general meeting once the Company has received requests from its members to do so in accordance with the Companies Act.

Notice of general meetings shall include all information required to be included by the Companies Act and shall be given to all members other than those members who are not entitled to receive such notices from the Company under the provisions of the Articles. The Company may determine that only those persons entered on the Register at the close of business on a day decided by the Company, such day being no more than 21 days before the day that notice of the meeting is sent, shall be entitled to receive such a notice.

For the purposes of determining which persons are entitled to attend or vote at a meeting, and how many votes such persons may cast, the Company must specify in the notice of the meeting a time, not more than 48 hours before the time fixed for the meeting, by which a person must be entered on the Register in order to have the right to attend or vote at the meeting. The directors may in their discretion resolve that, in calculating such period, no account shall be taken of any part of any day that is not a working day (within the meaning of Section 1173 of the Companies Act).

No business other than the appointment of a chairman of the meeting shall be transacted at any general meeting unless a quorum is present at the time when the meeting proceeds to business. The necessary quorum at a general meeting shall be two persons entitled to vote upon the business to be transacted, each being a member or a proxy for a member or a duly authorized representative of a corporation which is a member (including for this purpose two persons who are proxies or corporate representatives of the same member), between them, holding or representing by proxy at least one-third in nominal value of the issued shares.

The directors may require attendees to submit to searches or put in place such arrangements or restrictions as they think fit to ensure the safety and security of attendees at a general meeting. Any member, proxy or other person who fails to comply with such arrangements or restrictions may be refused entry to, or removed from, the general meeting.

The directors may decide that a general meeting shall be held at two or more locations to facilitate the organization and administration of such meeting. A member present in person or by proxy at the designated “satellite” meeting place may be counted in the quorum and may exercise all rights that they would have been able to exercise if they had been present at the principal meeting place. The directors may make and change from time to time such arrangements as they shall in their absolute discretion consider appropriate to:

Our Articles do not restrict in any way the ownership or voting of our shares by non-residents. Furthermore, there is no longer an obligation of a shareholder of a U.K. company which is a non-listed (in the U.K. or EU) company to voluntarily disclose his or her shareholding unless, required to do so by the company. If the company serves a demand on a person under section 793 to the Companies Act, that person will be required to disclose any interest he has in the shares of the company.

We can issue additional shares with any rights or restrictions attached to them as long as they are not restricted by any rights attached to existing shares. These rights or restrictions can be decided by the directors so long as there is no conflict with the Articles or any resolution passed by the shareholders. The ability of the directors to issue shares with rights or restrictions that are different than those attached to the currently outstanding shares could have the effect of delaying, deferring or preventing change of control of our Company.

We may in the future be subject to the U.K. Takeover Code, which is not binding on the Company at the present time. Nevertheless, the U.K. Takeover Code could apply to the Company under certain circumstances in the future and if that were to occur, if a person: (i) acquires an interest in our shares which, when taken together with shares in which he or her or a person acting in concert with him or her are interested, carries 30% or more of the voting rights of our shares, or (ii) who together with persons acting in concert with him or her, is interested in shares that in the aggregate carry not less than 30% and not more than 50% of the voting rights in the Company acquires additional interests in shares that increase the percentage of shares carrying voting rights in which that person is interested, in both cases, the acquirer and, depending on the circumstances its concert parties, would be required (except with the consent of the U.K. Takeover Panel), to make a cash offer for our outstanding shares at a price not less than the highest price paid for any interests in the shares by the acquirer or its concert parties during the previous 12 months.

Our shares are listed on the NASDAQ Global Select Market under the symbol “AY.”

The transfer agent and registrar for our ordinary shares is Computershare Trust Company, N.A.

The following description of the terms of the debt securities sets forth certain general terms and provisions of the debt securities to which any prospectus supplement may relate. The particular terms of the debt securities offered by any prospectus supplement and the extent, if any, to which these general provisions may apply to those debt securities will be described in the prospectus supplement relating to those debt securities. Accordingly, for a description of the terms of a particular issue of debt securities, reference must be made to both the prospectus supplement relating thereto and to the following description.

We may offer secured or unsecured debt securities which may be senior, subordinated or junior subordinated, and which may be convertible into equity. When we offer to sell a particular series of debt securities, we will describe the specific terms of that series in a supplement to this prospectus. The following description of debt securities will apply to the debt securities offered by this prospectus unless we provide otherwise in the applicable prospectus supplement. The applicable prospectus supplement for a particular series of debt securities may specify different or additional terms and to the extent the applicable prospectus supplement or other offering materials relating to an offering of debt securities are inconsistent with this prospectus, the terms of that prospectus supplement or other offering materials will supersede the information in this prospectus.

The debt securities offered hereby will be issued under one or more separate indentures between us and a designated trustee to be named in the indenture. The indenture will be qualified under, subject to, and governed by, the Trust Indenture Act of 1939, as amended.

The terms of each series of debt securities will be established by or pursuant to a resolution of our board of directors (and with respect to debt securities convertible into equity pursuant to an authorization or a resolution by the general meeting) and detailed or determined in the manner provided in a board of directors’ resolution, an officer’s certificate or by a one or more separate indentures. The particular terms of each series of debt securities that we may offer pursuant to this prospectus will be described in a prospectus supplement relating to the series, including any pricing supplement. These terms may include the following:

We may issue debt securities that are exchangeable and/or convertible into shares of our ordinary shares. The terms, if any, on which the debt securities may be exchanged for and/or converted will be set forth in the applicable prospectus supplement. Such terms may include provisions for conversion, either mandatory, at the option of the holder or at our option, in which case the number of shares of ordinary shares or other securities to be received by the holders of debt securities would be calculated as of a time and in the manner stated in the prospectus supplement. Neither the trustee nor the conversion agent shall have any duty to verify calculations respecting conversions. All such calculations shall be performed by us and our agents. Neither the trustee nor the conversion agent shall have any liability for not verifying our calculations and shall be entitled to rely upon them.

We may sell the debt securities, including original issue discount securities, at par or at a substantial discount below their stated principal amount. Unless we inform you otherwise in a prospectus supplement, we may issue additional debt securities of a particular series without the consent of the holders of the debt securities of such series outstanding at the time of issuance. Any such additional debt securities, together with all other outstanding debt securities of that series, will constitute a single series of securities under the applicable

indenture. In addition, we will describe in the applicable prospectus supplement material U.K. and U.S. federal income tax considerations and any other special considerations applicable to any of the related debt securities. For any debt securities we sell which are denominated in a currency or currency unit other than U.S. dollars, we will provide you with information on the restrictions, elections, general tax considerations, specific terms and other information with respect to that issue of debt securities and such foreign currency or currencies or foreign currency unit or units in the applicable prospectus supplement. Unless we inform you otherwise in the applicable prospectus supplement, the debt securities will not be listed on any securities exchange.

We expect most debt securities to be issued in fully registered form without coupons and in denominations of $1,000 and integral multiples thereof. Subject to the limitations provided in the indenture and in the prospectus supplement, debt securities that are issued in registered form may be transferred or exchanged at the corporate office of the trustee or the principal corporate trust office of the trustee, without the payment of any service charge, other than any tax or other governmental charge payable in connection therewith.

If specified in the applicable prospectus supplement, certain of our subsidiaries will guarantee the debt securities. The particular terms of any guarantee will be described in the related prospectus supplement.

Unless we inform you otherwise in the applicable prospectus supplement, the debt securities of a series may be issued in whole or in part in the form of one or more global securities that will be deposited with, or on behalf of, a depositary identified in the applicable prospectus supplement. Global securities will be issued in registered form and in either temporary or definitive form. Unless and until it is exchanged in whole or in part for the individual debt securities, a global security may not be transferred except as a whole by the depositary for such global security to a nominee of such depositary or by a nominee of such depositary to such depositary or another nominee of such depositary or by such depositary or any such nominee to a successor of such depositary or a nominee of such successor. The specific terms of the depositary arrangement with respect to any debt securities of a series and the rights of and limitations upon holders of beneficial interests in a global security will be described in the applicable prospectus supplement.

Unless we inform you otherwise in the applicable prospectus supplement, any indenture and the debt securities will be governed by, and construed in accordance with, the laws of the State of New York.

The following summary of certain provisions of the warrants does not purport to be complete and is subject to, and qualified in its entirety by reference to, the terms of the warrants that will be filed with the SEC in connection with the offering of such warrants.

We may issue warrants to purchase any of our securities or securities of third parties or other rights, including rights to receive payment in cash or securities based on the value, rate or price of one or more specified commodities, currencies, securities or indices, or any combination of the foregoing. Warrants may be issued independently or together with any other securities and may be attached to, or separate from, such securities. Each series of warrants may be issued under a separate warrant agreement to be entered into between us and the investor, a bank, a trust or other warrant agent. The terms of any warrants to be issued and a description of the material provisions of the applicable warrant agreement will be set forth in the applicable prospectus supplement.

The applicable prospectus supplement will describe the following terms of any warrants in respect of which this prospectus is being delivered, including:

Each debt security and warrant will be represented either by a certificate issued in definitive form to a particular investor or by one or more global securities representing the entire issuance of securities. Certificated securities in definitive form and global securities will be issued in registered form. Definitive securities name you or your nominee as the owner of the security, and in order to transfer or exchange these securities or to receive payments other than interest or other interim payments, you or your nominee must physically deliver the securities to the trustee, registrar, paying agent or other agent, as applicable. Global securities name a depositary or its nominee as the owner of the debt security or warrant represented by these global securities. The depositary maintains a computerized system that will reflect each investor’s beneficial ownership of the securities through an account maintained by the investor with its broker/dealer, bank, trust company or other representative, as we explain more fully below.

Registered Global Securities. We may issue the registered debt securities and warrants in the form of one or more fully registered global securities that will be deposited with a depositary or its nominee identified in the applicable prospectus supplement and registered in the name of that depositary or nominee. In those cases, one or more registered global securities will be issued in a denomination or aggregate denominations equal to the portion of the aggregate principal or face amount of the securities to be represented by registered global securities. Unless and until it is exchanged in whole for securities in definitive registered form, a registered global security may not be transferred except as a whole by and among the depositary for the registered global security, the nominees of the depositary or any successors of the depositary or those nominees.

If not described below, any specific terms of the depositary arrangement with respect to any securities to be represented by a registered global security will be described in the prospectus supplement relating to those securities. We anticipate that the following provisions will apply to all depositary arrangements.

Ownership of beneficial interests in a registered global security will be limited to persons, called participants, that have accounts with the depositary or persons that may hold interests through participants. Upon the issuance of a registered global security, the depositary will credit, on its book-entry registration and transfer system, the participants’ accounts with the respective principal or face amounts of the securities beneficially owned by the participants. Any dealers, underwriters or agents participating in the distribution of the securities will designate the accounts to be credited. Ownership of beneficial interests in a registered global security will be shown on, and the transfer of ownership interests will be effected only through, records maintained by the depositary, with respect to interests of participants, and on the records of participants, with respect to interests of persons holding through participants. The laws of some states may require that some purchasers of securities take physical delivery of these securities in definitive form. These laws may impair your ability to own, transfer or pledge beneficial interests in registered global securities.

So long as the depositary, or its nominee, is the registered owner of a registered global security, that depositary or its nominee, as the case may be, will be considered the sole owner or holder of the securities represented by the registered global security for all purposes under the applicable indenture or warrant agreement. Except as described below, owners of beneficial interests in a registered global security will not be entitled to have the securities represented by the registered global security registered in their names, will not receive or be entitled to receive physical delivery of the securities in definitive form and will not be considered the owners or holders of the securities under the applicable indenture or warrant agreement. Accordingly, each person owning a beneficial interest in a registered global security must rely on the procedures of the depositary for that registered global security and, if that person is not a participant, on the procedures of the participant through which the person owns its interest, to exercise any rights of a holder under the applicable indenture or warrant agreement. We understand that under existing industry practices, if we request any action of holders or if an owner of a beneficial interest in a registered global security desires to give or take any action that a holder is entitled to give or take under the applicable indenture or warrant agreement, the depositary for the registered global security would authorize the participants holding the relevant beneficial interests to give or take that action, and the participants would authorize beneficial owners owning through them to give or take that action or would otherwise act upon the instructions of beneficial owners holding through them.

Principal, premium, if any, and interest payments on debt securities, and any payments to holders with respect to warrants, represented by a registered global security registered in the name of a depositary or its

nominee will be made to the depositary or its nominee, as the case may be, as the registered owner of the registered global security. None of Atlantica, the trustees or the warrant agents, or any other agent of Atlantica, agent of the trustees or agent of the warrant agents, will have any responsibility or liability for any aspect of the records relating to payments made on account of beneficial ownership interests in the registered global security or for maintaining, supervising or reviewing any records relating to those beneficial ownership interests.

We expect that the depositary for any of the securities represented by a registered global security, upon receipt of any payment of principal, premium, interest or other distribution of underlying securities or other property to holders on that registered global security, will immediately credit participants’ accounts in amounts proportionate to their respective beneficial interests in that registered global security as shown on the records of the depositary. We also expect that payments by participants to owners of beneficial interests in a registered global security held through participants will be governed by standing customer instructions and customary practices, as is now the case with the securities held for the accounts of customers in bearer form or registered in “street name,” and will be the responsibility of those participants.

If the depositary for any of these securities represented by a registered global security is at any time unwilling or unable to continue as depositary or ceases to be a clearing agency registered under the Securities Exchange Act of 1934 and a successor depositary registered as a clearing agency under the Securities Exchange Act of 1934 is not appointed by us within 90 days, we will issue securities in definitive form in exchange for the registered global security that had been held by the depositary. Any securities issued in definitive form in exchange for a registered global security will be registered in the name or names that the depositary gives to the relevant trustee, warrant agent or other relevant agent of ours or theirs. It is expected that the depositary’s instructions will be based upon directions received by the depositary from participants with respect to ownership of beneficial interests in the registered global security that had been held by the depositary.

Material United Kingdom and United States federal income tax consequences relating to the purchase, ownership and disposition of any of the securities offered by this prospectus will be set forth in the applicable prospectus supplement related to those securities.

The securities being offered by this prospectus may be sold from time to time in one or more of the following ways (or in any combination thereof):

At any time a particular offer of the securities covered by this prospectus is made, a revised prospectus or prospectus supplement, if required, will be distributed which will set forth:

Such prospectus supplement, and, if necessary, a post-effective amendment to the registration statement of which this prospectus is a part, will be filed with the SEC to reflect the disclosure of additional information with respect to the distribution of the securities covered by this prospectus. In order to comply with the securities laws of certain states, if applicable, the securities sold under this prospectus may only be sold through registered or licensed broker-dealers. In addition, in some states the securities may not be sold unless they have been registered or qualified for sale in the applicable state or an exemption from registration or qualification requirements is available and is complied with.

The distribution of securities may be effected from time to time in one or more transactions, including block transactions and transactions on NASDAQ or any other organized market where the securities may be traded. The securities may be sold at a fixed price or prices, which may be changed, or at market prices prevailing at the time of sale, at prices relating to the prevailing market prices or at negotiated prices. The consideration may be cash or another form negotiated by the parties. Agents, underwriters or broker-dealers may be paid compensation for offering and selling the securities. That compensation may be in the form of discounts, concessions or commissions to be received from us or from the purchasers of the securities. Any dealers and agents participating in the distribution of the securities may be deemed to be underwriters, and compensation received by them on resale of the securities may be deemed to be underwriting discounts. If any such dealers or agents were deemed to be underwriters, they may be subject to statutory liabilities under the Securities Act.

Agents may from time to time solicit offers to purchase the securities. If required, we will name in the applicable prospectus supplement any agent involved in the offer or sale of the securities and set forth any compensation payable to the agent. Any public offering price and any discounts or concessions allowed or reallowed or paid to dealers may be changed from time to time. Unless otherwise indicated in the prospectus supplement, any agent will be acting on a best efforts basis to solicit purchases for the period of its appointment or to sell securities on a continuing basis.

If underwriters are used in a sale, securities will be acquired by the underwriters for their own account and may be resold from time to time in one or more transactions, including negotiated transactions, at a fixed public offering price or at varying prices determined at the time of sale, or under delayed delivery contracts or other contractual commitments. Securities may be offered to the public either through underwriting syndicates

represented by one or more managing underwriters or directly by one or more firms acting as underwriters. If an underwriter or underwriters are used in the sale of securities, an underwriting agreement will be executed with the underwriter or underwriters, as well as any other underwriter or underwriters, with respect to a particular underwritten offering of securities, and will set forth the terms of the transactions, including compensation of the underwriters and dealers and the public offering price, if applicable. The prospectus and prospectus supplement will be used by the underwriters to resell the securities. We may change from time to time any public offering price and any discounts or concessions the underwriters allow or reallow or pay to dealers.

If a dealer is used in the sale of the securities, we or an underwriter will sell the securities to the dealer, as principal. The dealer may then resell the securities to the public at varying prices to be determined by the dealer at the time of resale. To the extent required, we will set forth in the prospectus supplement the name of the dealer and the terms of the transactions.

To facilitate any offering of securities, certain persons participating in the offering may engage in transactions that stabilize, maintain or otherwise affect the price of the securities. This may include over-allotments or short sales of the securities, which involve the sale by persons participating in the offering of more securities than the Company sold to them. In these circumstances, these persons would cover such overallotments or short positions by exercising their over-allotment option, if any, or making purchases in the open market. In addition, these persons may stabilize or maintain the price of the securities by bidding for or purchasing securities in the open market or by imposing penalty bids, whereby selling concessions allowed to dealers participating in the offering may be reclaimed if securities sold by them are repurchased in connection with stabilization transactions. The effect of these transactions may be to stabilize or maintain the market price of the securities at a level above that which might otherwise prevail in the open market. These transactions may be discontinued at any time.

Agents, underwriters and dealers may be entitled under agreements which may be entered into with us to indemnification by us against specified liabilities, including liabilities incurred under the Securities Act, or to contribution by us to payments they may be required to make in respect of such liabilities. If required, the prospectus supplement will describe the terms and conditions of the indemnification or contribution. Some of the agents, underwriters or dealers, or their affiliates may be customers of, engage in transactions with or perform services for us or our subsidiaries.

We may directly solicit offers to purchase the securities and may make sales of securities directly to institutional investors or others. In addition, ordinary shares may be issued upon conversion of or in exchange for debt securities or other securities. These persons may be deemed to be underwriters within the meaning of the Securities Act with respect to any resale of the securities. To the extent required, the prospectus supplement will describe the terms of any such sales, including the terms of any bidding or auction process, if used.

Any securities that qualify for sale pursuant to Rule 144 or Regulation S under the Securities Act or in another transaction exempt from or not subject to the registration requirements of the Securities Act, may be sold under Rule 144 or Regulation S rather than pursuant to this prospectus.

If so indicated in the applicable prospectus supplement, we may authorize underwriters, dealers or agents to solicit offers from certain types of institutional investors to purchase the offered securities from us at the public offering price set forth in the prospectus supplement pursuant to delayed delivery contracts providing for payment and delivery on a specified date in the future. Such contracts will be subject only to those conditions set forth in the prospectus supplement and the prospectus supplement will set forth the commission payable for solicitation of such contracts.

These transactions may be effected on an exchange or automated quotation system, if the securities are listed on that exchange or admitted for trading on that automated quotation system, or in the over-the-counter market or otherwise. Under the securities laws of some jurisdictions, the securities offered by this prospectus may be sold in those jurisdictions only through registered or licensed brokers or dealers.

Any person participating in the distribution of securities registered under the Registration Statement that includes this prospectus will be subject to applicable provisions of the Exchange Act, and the applicable SEC rules and regulations, including, among others, Regulation M, which may limit the timing of purchases and sales of any of our securities by that person. Furthermore, Regulation M may restrict the ability of any person engaged

in the distribution of our securities to engage in market-making activities with respect to our securities. These restrictions may affect the marketability of our securities and the ability of any person or entity to engage in market-making activities with respect to our securities.

To the extent that we make sales to or through one or more underwriters or agents in at-the-market offerings, we will do so pursuant to the terms of a distribution agreement between us and the underwriters or agents. If we engage in at-the-market sales pursuant to a distribution agreement, we will issue and sell our ordinary shares to or through one or more underwriters or agents, which may act on an agency basis or on a principal basis. During the term of any such agreement, we may sell ordinary shares on a daily basis in exchange transactions or otherwise as we agree with the underwriters or agents. The distribution agreement will provide that any ordinary shares sold will be sold at prices related to the then prevailing market prices for our ordinary shares. Therefore, exact figures regarding proceeds that will be raised or commissions to be paid cannot be determined at this time and will be described in a prospectus supplement. Pursuant to the terms of the distribution agreement, we also may agree to sell, and the relevant underwriters or agents may agree to solicit offers to purchase, blocks of our ordinary shares or other securities. The terms of each such distribution agreement will be set forth in more detail in a prospectus supplement to this prospectus.

We may enter into derivative transactions with third parties or sell securities not covered by this prospectus to third parties in privately negotiated transactions. If the applicable prospectus supplement indicates, in connection with those derivatives, such third parties (or affiliates of such third parties) may sell securities covered by this prospectus and the applicable prospectus supplement, including in short sale transactions. If so, such third parties (or affiliates of such third parties) may use securities pledged by us or borrowed from us or others to settle those sales or to close out any related open borrowings of shares, and may use securities received from us in settlement of those derivatives to close out any related open borrowings of shares. The third parties (or affiliates of such third parties) in such sale transactions will be underwriters and, if not identified in this prospectus, will be identified in the applicable prospectus supplement (or a post-effective amendment).

We may loan or pledge securities to a financial institution or other third party that in turn may sell the securities using this prospectus. Such financial institution or third party may transfer its short position to investors in our securities or in connection with a simultaneous offering of other securities offered by this prospectus or in connection with a simultaneous offering of other securities offered by this prospectus. In addition, underwriters and agents may be customers of, engage in transactions with or perform services for us and our affiliates in the ordinary course of business.

Unless otherwise indicated in the applicable prospectus supplement, the validity of the securities, certain legal matters in connection with this prospectus relating to New York law and English law will be passed upon by Skadden, Arps, Slate, Meagher & Flom (UK) LLP.

The consolidated financial statements of Atlantica Sustainable Infrastructure plc at December 31, 2020 and 2019, and for each of the two years in the period ended December 31, 2020, appearing in Atlantica Sustainable Infrastructure plc’s Annual Report on Form 20-F for the year December 31, 2020, and the effectiveness of Atlantica Sustainable Infrastructure plc’s internal control over financial reporting as of December 31, 2021, have been audited by Ernst & Young S.L., an independent registered public accounting firm, set forth in their reports thereon, included therein, and incorporated herein by reference. Such consolidated financial statements are, and the audited financial statements to be included in subsequently filed documents will be, incorporated herein by reference in reliance upon such reports of Ernst & Young, S.L. pertaining to such financial statements and the effectiveness of our internal control over financial reporting as of the respective dates (to the extent covered by consents filed with the Securities and Exchange Commission) given on the authority of such firm as experts in accounting and auditing.

The consolidated financial statements as of and for the year ended December 31, 2018, incorporated in this prospectus by reference to the Company’s Annual Report on Form 20-F for the year December 31, 2020, have been audited by Deloitte, S.L., an independent registered public accounting firm, as stated in their report appearing therein, and incorporated herein by reference. Such consolidated financial statements are incorporated herein by reference in reliance upon the report of such firm given on the authority as experts in accounting and auditing.