Introduction

senior debt securities that the Company may offer, AGH may offer, Aon Corporation may offer, ANA may offer or that any combination of the Company, AGH, Aon Corporation or ANA may offer as co-issuers, (the foregoing debt securities or co-issued debt securities being, “Debt Securities”);

guarantees by the Registrants of the Debt Securities (“Guarantees”);

preference shares of $0.01 each (nominal value) in the capital of the Company (“Preference Shares”);

class A ordinary shares of $0.01 each (nominal value) in the capital of the Company (“A Ordinary Shares”, and together with the Preference Shares, “Shares”);

share purchase contracts, representing contracts obligating holders to purchase from the Company, and obligating the Company to sell, to the holders, a specified number of A Ordinary Shares at a future date or dates (“Share Purchase Contracts”); and

share purchase units, comprising a Share Purchase Contract, and, as security for a holder’s obligations to purchase A Ordinary Shares, co-issued debt securities, Preference Shares or debt obligations of third parties (including AGH debt securities, Aon Corporation debt securities, ANA debt securities and U.S. Treasury securities) (“Share Purchase Units”, and together with the Debt Securities, the Guarantees, the Preference Shares, the A Ordinary Shares and the Share Purchase Contracts, “Securities”).

a New York law governed form of indenture, filed with the Commission on 22 June 2023 as Exhibit 4.31 to the Company’s Registration Statement on Form S-3 (File No. 333-272818), to be made among AGH, as issuer or co-issuer, any of the Company, Aon Corporation or ANA, as co-issuer, and the Company, AGL, Aon Corporation and / or ANA, to the extent not acting as co-issuer, as guarantors, and The Bank of New York Mellon Trust Company, N.A., as trustee (the “AGH Indenture”), as supplemented, from time to time, by one or more, duly authorised, executed and lawful supplemental indentures;

a New York law governed form of amended and restated indenture filed with the Commission on 22 June 2023 as Exhibit 4.30 to the Company’s Registration Statement on Form S-3 (File No. 333-272818), to be made among Aon Corporation, as issuer or co-issuer, any of the Company, AGH or ANA, as co-issuer, and the Company, AGL, AGH and / or ANA, to the extent not acting as co-issuer, as guarantors, and The Bank of New York Mellon Trust Company, N.A., as trustee (the “Aon Corporation Indenture”), as supplemented, from time to time, by one or more, duly authorised, executed and lawful supplemental indentures; and

a New York law governed base indenture dated 1 March 2024, filed with the Commission on 1 March 2024 as Exhibit 4.1 to the Company’s Current Report on Form-8K, made among ANA, as issuer or co-issuer, any of the Company, AGH or Aon Corporation, as co-issuer, and the Company, AGL, AGH and / or Aon Corporation, to the extent not acting as co-issuer, as guarantors, and The Bank of New York Mellon Trust Company, N.A., as trustee (the “ANA Indenture”, and together with the Aon plc Indenture, the AGH Indenture and the Aon Corporation Indenture, the “Indentures”) as supplemented, from time to time, by one or more, duly authorised, executed and lawful supplemental indentures.

Basis of Opinion

Opinions

The Company is a public limited company, duly incorporated and validly existing under the laws of Ireland.

The Company has the requisite corporate power under its constitution, subject to it taking all necessary corporate action to authorise same (including a valid resolution of its board of directors or a duly constituted committee thereof), to enter into the Indentures and to perform its obligations thereunder, including to (i) co-issue Debt Securities and (ii) give Guarantees, in each case on the terms contained in the Indentures, as supplemented, from time to time, by one or more duly authorised, executed and lawful supplemental indentures, and such Debt Securities and Guarantees, when issued or given, as aforesaid, will constitute valid and binding obligations of the Company.

The Shares (including any Shares issued pursuant to Share Purchase Contracts and Share Purchase Units), when allotted and issued in accordance with the provisions of the Company’s constitution and all necessary corporate action of the Company (including a valid resolution of its board of directors or a duly constituted committee thereof) against receipt by the Company of the full consideration payable therefor, will, upon the entry of the name(s) of the relevant allottee(s) in the register of members of the Company as the registered holder(s) thereof (in each case credited as fully paid-up), be validly issued, fully paid-up and non-assessable. “Non-assessable” is a phrase which has no defined meaning under Irish law, but, for the purposes of this Opinion, shall mean the registered holders of such Shares are not subject, solely by virtue of their shareholdings, to calls for additional payments of capital on such shares). As a matter of Irish law, a share in an Irish incorporated company is only issued when it has been entered in the register of members of the relevant company.

The Company has the requisite power under its constitution, subject to it taking all necessary corporate action to authorise same (including a valid resolution of its board of directors or a duly constituted committee thereof), to enter into Share Purchase Contracts and Share Purchase Units, provided that any Debt Securities issued as part of any Share Purchase Units are issued in accordance with the terms of the Indentures, as supplemented, from time to time, by one or more duly authorised, executed and lawful supplemental indentures, and such Share Purchase Contracts and Share Purchase Units, when entered into or issued, as aforesaid, will constitute valid and binding obligations of the Company.

Reliance

Consent

Governing Law

The final form of the Registration Statement to which this Opinion is to be filed as an exhibit.

The final form of the Aon plc Indenture proposed to be filed with the Commission.

The forms of the AGH Indenture and the Aon Corporation Indenture filed with the Commission.

The ANA Indenture filed with the Commission.

A certificate issued by the secretary of the Company dated the date of this Opinion (the “Corporate Certificate”):

attaching a copy of each of the following documents certified as being true, complete and correct by the secretary:

the Company’s certificate of incorporation dated 23 May 2017, certificate of incorporation on change of name dated 5 November 2019 and certificate of incorporation on re-registration as a public limited company 18 March 2020 (the “Certificates of Incorporation”);

the memorandum of association of the Company adopted on 31 March 2020 (the “Memorandum of Association”) and the articles of association of the Company as amended on 2 June 2021 (the “Articles of Association”, and together with the Certificates of Incorporation and the Memorandum of Association, the “Constitutional Documents”); and

an extract of certain resolutions passed at a meeting of the board of directors of the Company held on 20 November 2025, (the “Board Resolutions’ Extract”); and

certifying certain other matters, as set out therein, on which we have relied for the purpose of this Opinion.

Searches carried out by independent law researchers on our behalf against the Company on the date of this Opinion: (a) in the Register of Winding-up Petitions maintained at the Central Office of the High Court of Ireland (the “Register of Winding-up Petitions”), (b) in the Judgments’ Office of the High Court of Ireland and (c) on the file of the Company maintained by the Registrar of Companies at the Irish Companies Registration Office (the “Companies Registration Office”) (together the “Searches”).

All signatures (including, for the avoidance of doubt, electronic signatures), initials, seals and stamps contained in, or on, any document examined by us are genuine.

All documents provided to us as originals are authentic and complete and all documents provided to us as copies (including, without limitation, any document provided to us as a .pdf (or any other format) attachment to an email) are complete and conform to the originals of such documents, and the originals of such documents are authentic and complete with all requisite seals and stamps affixed.

The contents of the documents (including the Corporate Certificate) and any other materials examined by us for the purposes of this Opinion are true and accurate as to factual matters, but we have made no independent investigation regarding such factual matters.

All documents dated on, or prior to, the date hereof and on which we have expressed reliance have not been revoked or amended and remain accurate.

Each natural person who has executed any document examined by us for the purposes of this Opinion had the due personal legal capacity to do so.

Any electronic signature inserted on a document was inserted by the signatory in question and not by another person and where attested by a witness was inserted in the physical presence of the witness. Each party to any document which has been executed using electronic signatures has consented to the execution of that document by way of electronic signature.

The Indentures have been, or will be, duly authorised, executed and delivered by all parties thereto in the forms we have examined for the purposes of this Opinion.

Any supplemental indenture to any of the Indentures will be duly authorised, executed and delivered by all parties thereto, and no such supplemental indenture will contain a term or other provision that would render the relevant Indenture or the offer, sale, issuance, admission to trading and / or listing of Securities or the giving of Guarantees thereunder unlawful under the Company’s constitution or the laws of any jurisdiction, including Ireland.

All offers, sales, issuances, admissions to trading and / or listing of Securities or the giving of Guarantees will conform to the description thereof in the prospectus or any prospectus supplement forming part of the Registration Statement.

There have been no amendments to the Constitutional Documents or the other attachments to the Corporate Certificate.

The resolutions documented in the Board Resolutions’ Extract were passed at a properly convened, constituted and quorate meeting of the board of directors of the Company, and such resolutions have not, since their date of adoption, been amended, superseded or rescinded and are in full force and effect.

The Company has derived, or will derive, a commercial benefit from entering into the Indentures, any supplemental indenture and any other document referred to in, or contemplated by, the Registration Statement (including the prospectus and any prospectus supplement forming part thereof), giving Guarantees and / or allotting and issuing, offering and / or selling any other Securities, in each case commensurate with the obligations undertaken by it thereunder.

In approving the entry into the Indentures, any supplemental indenture and any other document referred to in, or contemplated by, the Registration Statement (including the prospectus and any prospectus supplement forming part thereof), giving Guarantees and / or allotting and issuing, offering and / or selling any other Securities, the directors of the Company have acted, or will act, in good faith in the interests of the Company for the benefit of its members as a whole and for its legitimate business purposes.

In approving the entry into the Indentures, any supplemental indenture and any other document referred to in, or contemplated by, the Registration Statement (including the prospectus and any prospectus supplement forming part thereof), giving Guarantees and / or allotting and issuing, offering and / or selling any other Securities, each director of the Company has disclosed, or shall disclose, any interest which he or she may have in the relevant transactions in accordance with the provisions of the Companies Act 2014 of Ireland, as amended (the “Companies Act”) and the Company’s constitution.

No director or secretary of the Company is the subject of any declaration, order or deemed order for disqualification or restriction under the Companies Act, including Chapters 3 and 4 of Part 14 thereof, and no such person has received any notice under the Companies Act regarding a disqualification or restriction undertaking.

The Company together with any other entity whose obligations are guaranteed by it under the Indentures or any supplemental indenture together comprise a “group” for the purposes of section 243 of the Companies Act, and any person that subsequently becomes an issuer or a guarantor under the Indentures or any such supplemental indenture will also be a member of such group.

The Company will not, by virtue of entering into the Indentures, any supplemental indenture or any other document referred to in, or contemplated by, the Registration Statement (including the prospectus and any prospectus supplement forming part thereof), giving Guarantees and / or allotting and issuing, offering and / or selling any other Securities, give any financial assistance (as contemplated by sections 82 and 1043 of the Companies Act) for the purpose of the acquisition of any Shares, save as permitted by, or pursuant to an exemption from the application of, the said sections 82 and 1043.

The Company will have received the full consideration payable for any Shares prior to, or simultaneous with, their allotment and issue, and no Share will be allotted and issued for consideration that is less than its nominal value.

At the time of the allotment and issue of any Shares, the Company will have a sufficient number of unissued ordinary shares in its authorised share capital, being at least equal to the number of Shares to be allotted and issued.

At the time of the allotment and issue of any Shares or, if earlier, the granting of any rights to subscribe for, to receive or to convert any other Securities into, Shares (“Rights”, which shall include rights granted pursuant to Share Purchase Contracts and Share Purchase Units), to the

To the extent any Shares are being re-allotted off-market from treasury, the maximum and minimum prices of re-issue shall have been determined in advance at a general meeting of the Company in accordance with the requirements of section 1078 of the Companies Act.

No Shares will be allotted and issued for consideration that: (a) consists of an undertaking given by any person that he, she or another should do work or perform services for the Company or any other person, (b) includes an undertaking which is to be or may be performed more than five years after the date of the allotment or (c) is not considered good or adequate at law.

No Shares will be allotted or issued fully or partly paid-up otherwise than in cash unless the provisions of section 1028 of the Companies Act 2014 are complied with in full. Subject to certain exclusions, section 1028 requires that a valuation and report in respect of any non-cash consideration be prepared by an independent person and circulated to the proposed allottee(s).

Each person to whom Shares are allotted and issued will have the due and requisite capacity (and, if relevant, will have taken all necessary corporate action to be authorised) to be allotted and issued Shares (including upon the exercise or vesting of Rights) and to be registered in the register of members of the Company as the holder thereof. Each such person shall have consented, or will be deemed to have consented, to becoming a member of the Company.

To the extent any Shares to be allotted and issued are proposed to be issued directly to Cede & Co., as the nominee of The Depository Trust Company (“DTC”), the Company will have satisfied all requirements of DTC for acceptance of the Shares as eligible for its depository and book entry transfer services.

Each person expressed to be a party to an Indenture (other than the Company):

is, and shall continue to be, duly incorporated and validly existing;

is not, and shall not be, the subject of any insolvency proceedings (which includes those relating to bankruptcy, liquidation, examinership, rescue process, administration, receivership and reorganisation) in any jurisdiction;

had, or shall have, at the time it entered, or shall enter, into the Indenture, the due and requisite capacity to enter into and execute the Indenture and had, or shall have, at such time, and shall continue to have, the due and requisite capacity to perform the obligations it is expressed to assume under it;

has, or shall have, taken all necessary corporate action to authorise it to execute the Indenture and to perform the obligations it is expressed to assume under it;

has, or shall have, complied with and will comply with all the laws and regulations applicable to the transactions contemplated by the Indenture in any jurisdiction; and

has, or shall have, duly executed the Indenture.

The information disclosed by the Searches was accurate and complete as of the date the Searches were made and has not been altered. The Searches did not fail to disclose any information which had been delivered for registration but which did not appear from the information available at the time the Searches were made or which ought to have been delivered for registration at that time but had not been so delivered. No additional matters would have been disclosed by additional searches being carried out since that time.

The Company is at the date hereof, and will be at the time of and immediately following: (a) the execution and delivery of any Indenture or supplemental indenture, (b) giving any Guarantee, and (c) the allotment and issue, offer or sale of any other Securities, solvent.

The Company will not be insolvent as a consequence of: (a) executing and delivering any Indentures or supplemental indenture, (b) giving any Guarantee, (c) allotting and issuing, offering and / or selling any other Securities, and / or (d) doing any other act or thing referred to in, or contemplated by, the Registration Statement (including the prospectus and any prospectus supplement forming part thereof).

The Company has not at the date hereof, and will not have at the time of and immediately prior to: (a) the execution and delivery of any Indenture or any supplemental indenture, (b) giving any Guarantee, and (c) the allotment and issue, offer or sale of any other Securities, passed a voluntary winding-up resolution or a resolution to place the Company under court protection or to appoint a process adviser, and no petition has or will have been presented to, or order has or will have been made by, a court for the winding-up of the Company or to place the Company under court protection or for the appointment of a process adviser.

In approving the giving of any Guarantee or the allotment and issue, offer or sale of any other Securities, there shall be no intent by the Company to give a creditor a preference which could be deemed an unfair preference in accordance with section 604 of the Companies Act.

The obligations expressed to be assumed by each party to an Indenture, will upon the Indenture being authorised, executed and delivered, constitute legal, valid, binding and enforceable obligations under all applicable laws and in all applicable jurisdictions (other than, in the case of the Company, the laws of Ireland and the jurisdiction of Ireland) and any obligations expressed to be assumed by each party to any supplemental indenture and any other document referred to in, or contemplated by, the Registration Statement (including the prospectus and any prospectus supplement forming part thereof) will, upon such supplemental indenture or other document being authorised, executed and delivered, constitute legal, valid, binding and enforceable obligations under all applicable laws and in all applicable jurisdictions (including the laws of Ireland and the jurisdiction of Ireland).

If any obligation of any of the parties under an Indenture, any supplemental indenture or any other document referred to in, or contemplated by, the Registration Statement (including the prospectus and any prospectus supplement forming part thereof) is to be performed in any jurisdiction other than Ireland, its performance will not be illegal or ineffective by virtue of the law of that jurisdiction.

There are no provisions of the laws or public policy of any jurisdiction outside Ireland which would be contravened by the execution or performance of any Indenture, any supplemental indenture or any other document referred to in, or contemplated by, the Registration Statement (including the prospectus and any prospectus supplement forming part thereof) or which would render their performance ineffective by virtue of the laws of that jurisdiction.

The allotment and issue, offer and sale of any Securities, the giving of any Guarantees and any transfers and payments to be made thereunder or in connection therewith are not, and will not be, affected or prohibited by any financial restrictions or sanctions imposed by the United Nations, the European Union or Ireland or which arise under any human rights, anti-terrorism, anti-corruption, anti-money laundering or exchange control laws and regulations of the European Union or Ireland, including, without limitation, any arising from orders made under the Financial Transfers Act 1992 of Ireland, the Criminal Justice (Terrorist Offences) Acts 2005 and 2015 of Ireland or the Criminal Justice (Money Laundering and Terrorist Financing) Acts 2010 to 2021 of Ireland.

All authorisations, approvals, licences, exemptions or consents of governmental or regulatory authorities, including Ireland, with respect to the transactions contemplated by the Registration Statement (including the prospectus and any prospectus supplement forming part thereof), the giving of Guarantees and / or the allotment and issue, offer and / or sale of any other Securities have been, or will be, obtained and are, or will be, in full force and effect, and the selling restrictions contained in the Registration Statement (including the prospectus and any prospectus supplement forming part thereof) have been and will, at all times, be observed.

The allotment and issue, offer and / or sale (including the marketing) of any Securities will be made, effected and conducted in accordance with and will not otherwise violate: (a) any applicable securities laws and regulations of any jurisdiction (including the jurisdiction of Ireland) which impose any restrictions or mandatory requirements in relation to the offering or sale of any Securities to the public, including the obligation to prepare a prospectus or registration document relating to any Securities and (b) any requirement or restriction imposed by any court, governmental body or regulatory authority having jurisdiction over the Company or the members of its group.

No Securities will be listed or traded on a stock exchange or other market in the European Economic Area.

The absence of fraud and the presence of good faith on the part of all parties to any document we have examined for the purposes of this Opinion and their respective officers, employees, agents and advisors.

A search in the Companies Registration Office will not reveal whether a petition has been presented to the Irish courts for the appointment of a liquidator or an examiner.

A search of the Register of Winding-up Petitions should reveal the existence of a petition for the appointment of a liquidator or an examiner but there may be a time lag between presentation and entry of particulars of the petition on the Register of Winding-up Petitions and accordingly a search of the Register of Winding-up Petitions may fail to reveal that any such petition has been presented. Furthermore in the case of certain smaller companies a petition for the appointment of an examiner may be presented to the Circuit Court and a search of the Register of Winding-up Petitions will not reveal the existence of such a petition.

A search in the Companies Registration Office should reveal the appointment of a liquidator, examiner, process adviser or receiver (whether by the Irish courts or, in the case of a liquidator, process adviser or a receiver, out of court). However, similarly there may be a time lag between the appointment and the filing of particulars of the appointment and accordingly a search in the Companies Registration Office may fail to reveal any such appointment.

The expressions “valid” and “binding” and any variations thereof, when used in Section 3 (Opinions) mean that the obligations expressed to be assumed under an agreement are of a type which the courts of Ireland will treat as valid, binding and enforceable. It does not mean that these obligations will necessarily be enforced in all circumstances in accordance with their terms. In particular, enforcement of obligations under an agreement may be:

limited by general principles of equity, in particular, equitable remedies (such as an order for specific performance or an injunction) which are discretionary and are not available where damages are considered to be an adequate remedy;

subject to any limitations arising from examinership, administration, bankruptcy, insolvency, moratoria, receivership, liquidation, reorganisation, court scheme of arrangement, arrangement and similar laws affecting the rights of creditors;

limited by the provisions of the law of Ireland applicable to contracts held to have been frustrated by events happening after their execution;

invalidated if and to the extent that performance or observance arising in a jurisdiction outside Ireland would be unlawful, unenforceable, or contrary to public policy or to the exchange control regulations under the law of such jurisdiction;

invalidated by reason of fraud; and / or

barred under the Statutes of Limitations or may be or become subject to the defence of set-off or counterclaim.

The Companies Act prohibits certain steps being taken, except with the leave of the High Court, against a company after the presentation of a petition for the appointment of an examiner. This prohibition continues for so long as the examiner remains appointed. An examiner may remain

Under the provisions of the Companies Act, an examiner can also be appointed on a petition to the Circuit Court, if certain criteria are met. It is not possible for anyone other than a party to the relevant proceedings or the solicitors on record for such parties to inspect the Circuit Court files to ascertain whether a petition for the appointment of an examiner has been made in the Circuit Court, and we have made no searches or enquiries in this regard in respect of the Company.

A contractual provision conferring or imposing a remedy or an obligation consequent upon default may not be enforceable if it were construed by an Irish court as being a penalty, particularly if it involved enforcing an additional pecuniary remedy (such as a default or overdue interest) referable to such default and which does not constitute a genuine and reasonable pre-estimate of the damage likely to be suffered as a result of the default in payment of the amount in question or the termination in question; further, recovery may be limited by laws requiring mitigation of loss suffered.

An Irish court may not give effect to an indemnity given by any party in an agreement or other document to the extent it is in respect of legal costs incurred by an unsuccessful litigant or to the extent that it is in respect of litigation costs which are not awarded by the court.

In the event of any proceedings being brought in an Irish court in respect of a monetary obligation expressed to be payable in a currency other than euro an Irish court would have the power to give a judgment to pay a currency other than euro, it may decline to do so in its discretion and an Irish court might not enforce the benefit of currency conversion or indemnity clauses and, with respect to a bankruptcy, liquidation, insolvency, reorganisation or similar proceeding, the law of Ireland may require that all claims or debts are converted into euro at an exchange rate determined by the court as at a date related thereto, such as the date of commencement of a winding up.

A determination or calculation of any party to an agreement stated in that agreement to be conclusive may be held by the courts of Ireland not to be final, conclusive or binding.

The effect of terms, if any, in an agreement excusing a party from a liability or duty otherwise owed are limited by law.

Where a party is vested with a discretion or may determine a matter in his or its opinion, the laws of Ireland may require that such discretion is exercised reasonably or that such opinion is based upon reasonable grounds.

The courts of Ireland may interpret restrictively any provision purporting to allow the beneficiary of a guarantee or other suretyship to make a material amendment to the obligations to which the guarantee or suretyship relates without further reference to the guarantor or surety.

The enforceability of any provision as to severability may be determined by the courts of Ireland at its discretion.

No opinion is expressed on the irrevocability of any power of attorney.

An Irish court may not give effect to any provision of an agreement which (a) provides for a matter to be determined by future agreement or negotiation or (b) it considers to be devoid of any meaning, vague or uncertain.

A right of set-off provided for in a contract or another document may not be enforceable in all circumstances.