United States: Professional body rules | Research Credit Integrity Alliance

In the United States the people who prepare research credit claims may hold different credentials, and each credential comes with its own conduct rules. This page sets out what the professional rules for certified public accountants say about contingent fees, and how they sit alongside Treasury's Circular 230. The AICPA rule is covered in more detail on United States: AICPA Rule 1.510.

Who sets the rules

The IRS describes three credentials that carry unlimited rights to represent clients before it:1

Certified public accountants are licensed by state boards of accountancy, the District of Columbia and US territories, and must comply with ethical requirements to keep an active license.
Attorneys are licensed by state courts, the District of Columbia or their designees, such as the state bar.
Enrolled agents are licensed by the IRS.

All three, when practicing before the IRS, are practitioners under Circular 230, Treasury's rules of practice.2 Circular 230's contingent fee rule is described on United States: Fee rules.

The American Institute of CPAs (AICPA) publishes a Code of Professional Conduct for its members. The Code defines a member as a member, associate member, affiliate member or international associate of the AICPA, and when the term is used in Part 1 of the Code it means a member in public practice.3

The AICPA Contingent Fees Rule

The AICPA's Contingent Fees Rule, at ET 1.510.001, has two parts. The first bars a member in public practice from performing any professional services for a contingent fee for a client for whom the member or firm performs an audit or review of financial statements, certain compilations, or an examination of prospective financial information. The second is the tax rule. A member in public practice shall not:4

Prepare an original or amended tax return or claim for a tax refund for a contingent fee for any client.

The Code defines a contingent fee as a fee for any service under an arrangement in which no fee will be charged unless a specified finding or result is attained, or in which the amount of the fee otherwise depends on the finding or result. Fees are not regarded as contingent if fixed by courts or other public authorities or, in tax matters, if determined based on the results of judicial proceedings or the findings of governmental agencies.4 The rule adds that a member's fees may vary depending, for example, on the complexity of the services.4

The tax matters interpretation

An interpretation, ET 1.510.010, explains how the rule applies to tax work.5

Preparing a return or refund claim includes giving advice on events that have already occurred, if the advice is directly relevant to determining the existence, character or amount of a schedule, entry or other portion of the return or claim.
A fee is treated as based on the findings of a governmental agency, and so not contingent, if the member can show a reasonable expectation, when the fee is agreed, that a government agency will give substantive consideration to the matter. That expectation is not reasonable where the member prepares the client's original return.
The interpretation gives examples where a contingent fee is permitted. They include representing a client in a revenue agent's examination, and filing an amended return claiming a refund larger than the threshold for review by the Joint Committee on Taxation.
It gives one example where a contingent fee is not permitted: an amended return claiming a refund because a valid deduction was inadvertently omitted from the original return.
When practicing before the IRS or other taxing authorities, members should also comply with other applicable and more restrictive requirements.

Other parts of the Code

The Code's conceptual framework lists, as an example of a self-interest threat, a firm entering into a contingent fee arrangement for a tax refund claim that is not a predetermined fee.6 Where no interpretation addresses a circumstance, a member should apply that framework, and a member would be in violation of the Contingent Fees Rule if the member cannot show that safeguards eliminated or reduced significant threats to an acceptable level.7 A contingent fee is considered received when the member has completed the related services and the fee is determined.7

State accountancy rules

CPA licenses are issued by the states.1 In its December 2024 notice of proposed rulemaking, Treasury stated that many state accountancy board rules also prohibit contingent fee arrangements for preparing an original or amended return or claim for refund or credit, citing rules in New Jersey, Tennessee and California among others.8 This page does not summarize individual state rules.

How the rules compare

Point	AICPA Code (ET 1.510)	Circular 230 (31 CFR 10.27)
Who it binds	AICPA members in public practice	Practitioners before the IRS
Original return for a contingent fee	Not permitted	Not permitted
Amended return or refund claim for a contingent fee	Not permitted, unless the fee is based on the findings of a governmental agency as the Code defines	Not permitted, except in connection with an IRS examination or challenge, as the rule defines; limited for pre-audit refund claims by Ridgely v. Lew
Representation in an examination	Contingent fee permitted (example)	Contingent fee permitted
Refund claim above the Joint Committee review threshold	Contingent fee permitted (example)	No equivalent exception in the text

Sources for the table: the AICPA Code,4 5 Circular 230 section 10.279 and the Ridgely v. Lew opinion.10

What these rules do not cover

The AICPA Code binds AICPA members. Circular 230 binds practitioners. The IRS states that any tax professional with a preparer tax identification number is authorized to prepare federal tax returns, and that a preparer with no professional credential who does not take part in the Annual Filing Season Program has no authority to represent clients before the IRS.1 The court in Ridgely v. Lew noted that, on the IRS's own reading, section 10.27 would impose no contingent fee restrictions on the preparation and filing of ordinary refund claims by those who never practice before the IRS.10

Sources

Internal Revenue Service, Understanding tax return preparer credentials and qualifications, sections "Unlimited representation rights" and "PTIN holders" (page last reviewed or updated 29 January 2026). https://www.irs.gov/tax-professionals/understanding-tax-return-preparer-credentials-and-qualifications (accessed 11 October 2026). Back
Treasury Department, Circular No. 230, 31 CFR 10.3, Who may practice, paragraphs (a) to (c), read with 31 CFR 10.2(a)(5). https://www.ecfr.gov/current/title-31/subtitle-A/part-10/subpart-A/section-10.3 (accessed 11 October 2026). Back
American Institute of CPAs, Code of Professional Conduct (updated for all official releases through September 2026), ET 0.400, Definitions, paragraph .33 (Member). https://pub.aicpa.org/codeofconduct/ethicsresources/et-cod.pdf (accessed 11 October 2026). Back
American Institute of CPAs, Code of Professional Conduct (updated for all official releases through September 2026), ET 1.510.001, Contingent Fees Rule, paragraphs .01, .03 and .04. https://pub.aicpa.org/codeofconduct/ethicsresources/et-cod.pdf (accessed 11 October 2026). Back
American Institute of CPAs, Code of Professional Conduct (updated for all official releases through September 2026), ET 1.510.010, Tax Matters, paragraphs .01 to .05. https://pub.aicpa.org/codeofconduct/ethicsresources/et-cod.pdf (accessed 11 October 2026). Back
American Institute of CPAs, Code of Professional Conduct (updated for all official releases through September 2026), ET 1.000.010, Conceptual Framework for Members in Public Practice, paragraph .14c. https://pub.aicpa.org/codeofconduct/ethicsresources/et-cod.pdf (accessed 11 October 2026). Back
American Institute of CPAs, Code of Professional Conduct (updated for all official releases through September 2026), ET 1.510.005, paragraphs .01 and .02, and ET 1.510.020, paragraph .01. https://pub.aicpa.org/codeofconduct/ethicsresources/et-cod.pdf (accessed 11 October 2026). Back
Treasury Department and Internal Revenue Service, Regulations Governing Practice Before the Internal Revenue Service, notice of proposed rulemaking, 89 FR 104915 (26 December 2024), Explanation of Provisions part B and accompanying notes. https://www.federalregister.gov/documents/2024/12/26/2024-29371/regulations-governing-practice-before-the-internal-revenue-service (accessed 11 October 2026). Back
Treasury Department, Circular No. 230, 31 CFR 10.27, Fees, paragraphs (b) and (c) (eCFR text up to date as of 8 October 2026). https://www.ecfr.gov/current/title-31/subtitle-A/part-10/subpart-B/section-10.27 (accessed 11 October 2026). Back
US District Court for the District of Columbia, Ridgely v. Lew, Civil Action No. 1:12-cv-00565 (CRC), Memorandum Opinion, 16 July 2014, pages 1 and 12 to 15. https://www.govinfo.gov/content/pkg/USCOURTS-dcd-1_12-cv-00565/pdf/USCOURTS-dcd-1_12-cv-00565-1.pdf (accessed 11 October 2026). Back