IRS Circular 230: A CPA's Complete Guide to Practice Ethics and Professional Responsibilities

Treasury Department Circular No. 230 — codified at 31 CFR Part 10 and issued under 31 U.S.C. §330 — governs every CPA, attorney, enrolled agent, and credentialed practitioner who practices before the IRS. It establishes mandatory ethical standards for client representation, tax return positions, written advice, and conflicts of interest. Unlike state CPA ethics rules, which vary by jurisdiction, Circular 230 is a federal framework with a single enforcer: the IRS Office of Professional Responsibility (OPR). Violations can result in censure, suspension, or permanent disbarment from IRS practice — independent of any state board action. For CPAs who represent clients in examinations, respond to IRS notices, prepare complex business returns, or issue written tax opinions, understanding Circular 230 is a prerequisite, not a specialty topic.

Who Is Subject to Circular 230 — and What Counts as Practice

Circular 230 applies to "practitioners" — defined under 31 CFR §10.2(a)(5) as attorneys, CPAs, enrolled agents (EAs), enrolled retirement plan agents (ERPAs), and enrolled actuaries admitted to practice before the IRS. Practice before the IRS under §10.2(a)(4) includes all matters relating to a client's rights, privileges, or liabilities: preparing or filing tax documents, corresponding with the IRS, representing clients in conferences and hearings, and providing written advice with federal tax implications that could affect a specific client.

What is not considered practice before the IRS: Appearing as a witness at proceedings, furnishing information at IRS request, and certain ministerial acts — such as transmitting documents without providing substantive tax advice — fall outside the definition. Critically, the D.C. Circuit's 2014 decision in Loving v. IRS, 742 F.3d 1013 (D.C. Cir. 2014), held that the IRS lacked statutory authority to impose testing and registration requirements on unenrolled tax return preparers who are not CPAs, attorneys, or EAs. The practical implication: Circular 230 obligations — including competence requirements and OPR penalty exposure — apply to credentialed practitioners; non-credentialed preparers face a narrower set of return preparer penalty provisions under the Internal Revenue Code (IRC §§6694–6696).

State CPA ethics rules alongside Circular 230: State boards of accountancy impose independent ethical standards — AICPA Code of Professional Conduct, state-adopted variations, and continuing education requirements. A CPA may comply with Circular 230 and violate state rules, or vice versa. OPR sanctions do not trigger automatic state board action, though OPR typically reports sanctions to state boards. CPAs must track both frameworks.

Competence and Diligence Requirements

The competence standard under 31 CFR §10.35 requires practitioners to possess "the necessary competence to engage in practice before the Internal Revenue Service." This encompasses the appropriate level of knowledge, skill, thoroughness, and preparation necessary for the matter at hand.

What competence requires in practice:

• Technical knowledge adequate for the specific transaction, tax year, and entity type involved — a CPA competent to prepare simple individual returns may not be competent to structure a complex partnership or respond to a field examination involving transfer pricing
• Diligence in identifying and researching applicable tax authorities, including recent legislative changes, IRS guidance, and relevant Tax Court decisions
• Adequate preparation time — taking on more engagements than can be completed with reasonable diligence violates §10.35

Acquiring competence through consultation: §10.35 permits a practitioner who lacks the required competence to acquire it by (1) consulting with another practitioner who has the competence, (2) associating with a competent practitioner on the matter, or (3) declining the engagement. The obligation to decline where competence cannot be acquired is absolute — a practitioner cannot substitute effort for knowledge when the subject matter is outside their expertise.

The diligence standard under §10.22 requires that practitioners exercise due diligence in preparing, approving, and filing returns, documents, affidavits, and other papers relating to IRS matters; in determining the correctness of oral or written representations; and in determining that a client's documents are not being used to deceive the IRS. A CPA who signs a return without reviewing the underlying records is in violation of the §10.22 standard, regardless of whether the return is ultimately correct.

Tax Return Position Standards Under §10.34

The standard governing tax return positions applies to every business return a CPA prepares or signs. Under 31 CFR §10.34, a practitioner may not sign a return or advise a client to take a position unless the position:

1. Is not frivolous — meaning it has a good faith basis in law and fact
2. Is disclosed on the return if required by applicable regulations
3. Does not exploit the audit selection process as justification for a position that lacks legal support

The reasonable basis standard: For positions that are disclosed on the return via Form 8275 or Form 8275-R, the position must have at least a "reasonable basis" — generally understood as approximately a 20–33% probability of success. For undisclosed positions, the practitioner must have a reasonable belief that the position would more likely than not be sustained on its merits (a roughly 50% or better threshold). Disclosure is the mechanism that reduces the accuracy-related penalty under IRC §6662(d)(2)(B): a disclosed position with reasonable basis avoids the substantial understatement penalty even if the position is ultimately disallowed.

The obligation to advise on penalties: When a return position may result in an underpayment penalty if disallowed, the practitioner must advise the client of that penalty exposure before the return is filed. The advice must give the client enough information to make an informed decision — not a post-filing disclosure.

What §10.34 does not prohibit: A CPA may prepare a return containing a non-frivolous, properly disclosed position that the practitioner believes is unlikely to succeed. The obligation is to advise the client of the risk, not to refuse to file the return. A client who insists on a disclosed, legally non-frivolous position after being advised of the risk has received what Circular 230 requires.

Written Advice Standards Under §10.37

Written advice — emails, memos, formal opinion letters, and other written communications where a practitioner provides federal tax advice to a client — is governed by 31 CFR §10.37. The regulation requires that written advice:

1. Be based on reasonable factual and legal assumptions — the practitioner may rely on client-provided facts but must evaluate whether those facts are credible given the circumstances
2. Reasonably consider all relevant facts and circumstances
3. Apply the law in a way that is not frivolous — using the same reasonable basis standard that applies to return positions
4. Not be based on unreasonable reliance on representations — if the tax conclusion depends on a fact that seems implausible on its face, the practitioner cannot accept it without scrutiny

The 2014 revision: Treasury substantially revised §10.37 in 2014 to replace a complex "covered opinions" framework with a simpler, principles-based standard. The formal covered opinion analytical requirements were eliminated. The revised standard applies to substantive written communications — engagement letters with tax conclusions, email responses containing position recommendations, and written tax planning memos. The era of rote Circular 230 disclaimers on routine email correspondence largely ended with this revision; the obligation is now substantive analysis, not boilerplate disclosure.

Conflicts of Interest, Contingent Fees, and Solicitation

Conflicts of interest under §10.29: A practitioner may not represent a client before the IRS in a matter where the representation is directly adverse to another client's interests, or where there is a significant risk that the representation of one client will be materially limited by responsibilities to another client or a personal interest. A husband and wife with competing interests in a joint return audit, an S-Corp shareholder in a dispute with the corporation itself, or a CPA with a financial interest in a tax shelter being examined — all present §10.29 conflicts requiring disclosure and waiver, or withdrawal.

The waiver process: A conflict can be waived by informed written consent from each affected client after the conflict is disclosed — provided the practitioner reasonably believes they can still provide competent and diligent representation to each. If the conflict is so significant that competent representation of both clients is not possible, the conflict cannot be waived and the practitioner must withdraw from one or both representations.

Contingent fees under §10.27: Circular 230 generally prohibits contingent fee arrangements for preparing original tax returns and most IRS submissions. The prohibition does not apply to IRS examination and audit cases, claims for refund, or judicial proceedings where a contingent arrangement is permitted by the applicable rules of that proceeding.

Solicitation under §10.30: Circular 230 prohibits false, fraudulent, misleading, deceptive, or coercive advertising and requires that any endorsement or testimonial reflect genuine client experience. Direct solicitation to prospective clients who are currently represented by another practitioner in the same matter is prohibited unless that practitioner consents. Any advertised fixed fee must be available without qualification for the services as described. For market-rate benchmarks when establishing and advertising service fees, see CPA Fees and Hourly Rates in 2025.

Sanctions and the Office of Professional Responsibility

The IRS Office of Professional Responsibility (OPR) is the enforcement body for Circular 230 violations. OPR investigates practitioner conduct, initiates disciplinary proceedings, and imposes sanctions under 31 CFR §§10.50–10.82.

Available sanctions under §10.50:

What triggers OPR investigation: OPR initiates investigations based on referrals from IRS employees, complaints from clients or other practitioners, information developed during examination activity, and criminal conviction or professional sanction reports. Under §10.51(a), CPAs who have been convicted of a crime or disciplined by a state board must report that action to OPR within 30 days — failure to report independently constitutes a Circular 230 violation.

Practitioner responsibilities when clients make false statements: §10.52 identifies conduct subject to sanction, including willfully attempting to evade tax, willfully assisting a client in evading tax, and submitting false documents to the IRS. A CPA who discovers during an examination that a return they prepared contains false information must withdraw from representation. They cannot continue to advocate for the client while knowing the filed return is incorrect, even if the client insists on maintaining the position.

The practitioner's privilege under IRC §7525: CPAs have a limited statutory confidentiality privilege for tax advice in nontax criminal proceedings and non-criminal IRS administrative proceedings — but not in criminal tax investigations, criminal proceedings, or tax shelter matters. This privilege does not cover communications relating to tax return preparation and does not extend to tax advice that facilitates a crime or fraud. For how IRS contact types escalate from administrative notice to formal examination — and when referring clients to tax attorneys becomes appropriate — see IRS Audit Triggers and Defense: A CPA's Guide to Protecting Business Clients.

Building an Ethical Practice Framework

Circular 230 compliance is most reliably built into firm operations through structural practices rather than case-by-case assessment:

Engagement letters that establish scope and limits: Clearly defining what services are being provided, which returns the CPA is responsible for, and what information the client has certified as accurate limits §10.22 diligence exposure and creates a contemporaneous record. For clients with incomplete records or uncertain positions, note in the engagement letter that the return is being prepared based on information provided and that the client is responsible for accuracy. For the underlying document retention obligations that govern how long engagement records must be kept — and the CPA's obligations regarding client records upon termination of an engagement — see Document Retention Requirements for Business Clients: A CPA's Complete Guide.

Position memos for uncertain return positions: When a return contains a position that is legally supportable but uncertain, document the analysis in a written memo — the applicable authority, the basis for the position, the potential penalty exposure, and the advice given. This creates the contemporaneous record that satisfies §10.37 written advice standards and demonstrates §10.22 diligence if the position is later challenged.

Annual conflict-of-interest review: Before accepting a new matter for an existing client whose interests may conflict with another client, document the conflict analysis. Where a waiver is appropriate, document the informed consent in writing.

Staying current on OPR enforcement: OPR publishes disciplinary actions on the IRS website. Reviewing OPR enforcement actions annually is the most efficient way to understand where Circular 230 lines are drawn in current practice — and which conduct patterns the IRS is actively pursuing.

AI tools and the competence standard: As AI-assisted research and drafting tools enter CPA workflows, the §10.35 competence obligation requires that practitioners review and verify AI outputs before relying on them in client work or IRS submissions. A CPA who adopts an AI-generated tax conclusion without independent verification is not practicing with the thoroughness Circular 230 requires. For guidance on which AI workflows create §7216 disclosure obligations, how to evaluate vendors, and how to build a firm-wide AI policy that satisfies both Circular 230 and FTC Safeguards Rule requirements, see How to Use AI Tools Ethically in a CPA Practice.

FAQs

What is IRS Circular 230 and who does it apply to?

Circular 230 (Treasury Department Circular No. 230, 31 CFR Part 10) governs practice before the IRS. It applies to CPAs, attorneys, enrolled agents, enrolled retirement plan agents, and enrolled actuaries — any credentialed practitioner who prepares tax returns, represents clients in IRS proceedings, or provides federal tax advice in written form. Non-credentialed return preparers are not subject to Circular 230's practitioner requirements, though they face separate penalties under the Internal Revenue Code (IRC §§6694–6696).

What are the penalties for violating Circular 230?

The IRS Office of Professional Responsibility can impose censure (public or non-public), suspension from IRS practice, disbarment, and monetary penalties of up to $5,000 per violation or the gross income the practitioner derived from the violation — whichever is higher. OPR also reports sanctions to state boards of accountancy, which may trigger independent state disciplinary proceedings.

Can a CPA take an aggressive tax position on a client return under Circular 230?

Yes — provided the position is not frivolous, has at least a reasonable basis in law and fact, and the client has been advised of any potential penalty exposure. A disclosed, non-frivolous position with a reasonable basis satisfies §10.34 even if the CPA privately believes the position will ultimately fail. The obligation is accurate disclosure and informed client consent — not restricting the return only to positions the CPA is confident will succeed.

What is the difference between the reasonable basis and more-likely-than-not standards?

Under 31 CFR §10.34, an undisclosed tax return position requires a reasonable belief that the position would more likely than not be sustained — roughly a 50% or better confidence level. A disclosed position requires only a "reasonable basis" — generally understood as approximately 20–33% probability of success. Disclosure via Form 8275 or Form 8275-R satisfies the disclosure requirement, enables a lower threshold of confidence, and avoids the substantial understatement penalty under IRC §6662(d) even if the position is disallowed.

Is a CPA required to tell the IRS if a client's prior return contains an error?

No. A CPA has no affirmative obligation under Circular 230 to notify the IRS of a client's prior-year return errors. The obligation under §10.21 is to promptly advise the client of the error and the consequences of failing to correct it. If the client refuses to correct a material error, the CPA must withdraw from representing the client in the affected matter. The CPA may not file an amended return without the client's consent.

What is the difference between an OPR sanction and a return preparer penalty?

An OPR sanction is a disciplinary action against the practitioner's license to practice before the IRS — it affects professional standing, not the client's tax liability. A return preparer penalty under IRC §6694 or §6695 is a direct monetary assessment against the CPA for errors or misconduct on a client's return. Both can apply to the same underlying conduct: a CPA who willfully understates a client's tax liability may face both the §6694 penalty and an OPR disciplinary proceeding.

How does Circular 230 interact with responding to IRS notices?

When a CPA represents a client before the IRS — whether responding to a CP2000, a correspondence examination, or a field audit — Circular 230 governs the entire representation. The CPA must exercise competence, diligence, and candor; must not make false statements; and must withdraw if continuing the representation would require advancing a position known to be legally unsupportable. Filing a Form 2848 Power of Attorney initiates the formal representation relationship. For the step-by-step methodology for responding to IRS notices — including the CP2000 response process, examination types, and when matters escalate — see How to Respond to an IRS CP2000 Notice.

Does Circular 230 require CPAs to report a client who is committing tax fraud?

No. Circular 230 does not impose an affirmative duty to report clients to the IRS. The obligation is to withdraw from representation when continuing would assist the client in conduct the practitioner knows is fraudulent or misleading, and to advise the client to correct any error the CPA is aware of. The practitioner must not make false statements to the IRS on the client's behalf and cannot remain in a representation that requires doing so — but the obligation stops at withdrawal, not at reporting.

Arvori helps CPAs track client engagement obligations, manage examination response deadlines, and maintain the documentation standards required under IRS Circular 230 across their entire practice. Learn more at arvori.app.