Tax Specialists for US/UK Clients: CPA, EA, CTA or ATT Credentials — Who Does What?

Tax specialists for US/UK clients usually hold one of four credentials: a CPA (licensed by a US state board), an EA (licensed by the IRS), a CTA (awarded by the Chartered Institute of Taxation) or an ATT (awarded by the Association of Taxation Technicians). The US credentials carry IRS representation rights; the UK ones certify examined UK tax knowledge. No single one covers both countries.

That last point is the one most people miss. A cross-border return is two returns built on one set of facts, and each tax authority decides for itself who may act for you. This guide explains what each credential is, who issues it, what it lets the holder do, and how to check it yourself in a few minutes.

Why do credentials matter when choosing tax specialists for US/UK work?

Credentials matter because they decide what an adviser is allowed to do, not just what they know. On the US side, the right to represent you if the IRS examines a return depends entirely on holding a recognised credential. On the UK side, qualifications are voluntary, but a paid adviser dealing with HMRC must now be registered with HMRC.

Marketing copy tends to blur this. Phrases such as "our US team" or "qualified tax professionals" say nothing about who issued the qualification or what it permits. The four credentials below are the ones you will meet most often on cross-border engagements, and each is traceable to a named issuing body.

The US credentials: CPA and enrolled agent

Certified Public Accountant (CPA)

A Certified Public Accountant is licensed by a state board of accountancy, not by the federal government. The IRS guide to preparer credentials and qualifications describes CPAs as licensed by state boards of accountancy, the District of Columbia and US territories, having passed the Uniform CPA Examination and met education and experience requirements. The examination is developed by the American Institute of Certified Public Accountants (AICPA) and administered in partnership with the National Association of State Boards of Accountancy (NASBA), with the state boards deciding who is eligible and who is licensed.

A CPA licence is broad. It covers audit, financial reporting and advisory work as well as tax, so a CPA is not automatically a tax specialist. What the licence does give, for tax purposes, is unlimited practice rights before the IRS.

Enrolled agent (EA)

An enrolled agent is licensed directly by the IRS. The IRS says enrolled agents must pass a three-part Special Enrollment Examination covering individual and business tax and representation, or qualify through relevant former IRS employment. The EA is a tax-only credential, which is why it is common among preparers who focus on individual returns, including expat returns.

Enrolled agents must keep the credential current. According to the IRS page on maintaining enrolled agent status, an EA needs 72 hours of continuing education every three years (66 hours of qualifying CE plus 6 hours of ethics), with at least 16 hours a year, 2 of them on ethics. Renewal runs on a three-year cycle set by the last digit of the agent's Social Security Number, and the renewal window running from 1 October 2026 to 31 January 2027 applies to numbers ending in 7, 8 or 9.

What Circular 230 adds

Treasury Department Circular No. 230 is the set of regulations, at 31 CFR Part 10, that governs practice before the IRS. The IRS Circular 230 page explains that it sets standards of competence, diligence and ethical behaviour for practitioners, mainly attorneys, CPAs and enrolled agents, and that the Office of Professional Responsibility has exclusive delegated authority for practitioner conduct and discipline. In practical terms, a CPA or EA who acts for you is answerable to a federal regulator as well as to any licensing body.

The UK credentials: CTA and ATT

Chartered Tax Adviser (CTA)

The Chartered Tax Adviser qualification is awarded by the Chartered Institute of Taxation (CIOT). It is examined, advisory-level UK tax knowledge. CIOT states that regardless of how quickly students pass the exams, the CTA is not awarded until they have three years of relevant professional experience and have applied for membership of the Institute. Members are bound by the Institute's professional rules and continuing development requirements.

Association of Taxation Technicians (ATT)

The ATT qualification is awarded by the Association of Taxation Technicians and focuses on UK tax compliance: preparing returns and computations correctly. According to the Association, candidates pass papers in personal and business taxation, law, professional responsibilities and ethics, principles of accounting and one elective, and need two years' practical tax experience before applying for membership. Members use the letters ATT and the title Taxation Technician.

What UK qualifications do not do

Neither CTA nor ATT is a licence. The UK has no equivalent of Circular 230 that reserves representation before HMRC to credential holders, and many competent UK tax practitioners hold accountancy qualifications instead, such as those of the chartered accountancy bodies. What changed in 2026 is registration. GOV.UK guidance says that anyone who interacts with HMRC about someone else's tax affairs and gets paid for it must register as a tax adviser with HMRC through an agent services account, in staged windows, with three months to apply once a window opens. Registered agents are expected to meet the HMRC standard for agents.

Tax specialists for US/UK credentials compared side by side

The table sets the four credentials against each other. "Rights" means what the credential itself permits; a firm may hold further registrations on top.

Credential	Issued by	Covers	Rights it carries	Where to verify
CPA	US state boards of accountancy (exam by AICPA with NASBA)	Accounting, audit and tax	Unlimited representation before the IRS under Circular 230	The issuing state board, or NASBA CPAverify
Enrolled agent	IRS	US federal tax only	Unlimited representation before the IRS under Circular 230	IRS Office of Enrollment; IRS preparer directory
CTA	Chartered Institute of Taxation	UK tax, advisory level	No statutory rights; HMRC registration needed to act as a paid agent	CIOT member directory
ATT	Association of Taxation Technicians	UK tax compliance	No statutory rights; HMRC registration needed to act as a paid agent	ATT member directory

For a fuller walk-through of the questions to ask a firm beyond credentials, see our guide on how to choose US/UK cross border tax specialists.

How do you verify a tax adviser's credentials?

You verify a tax adviser's credentials with the body that issued them, never with the adviser's own website. Each check below takes a few minutes and uses a public tool or contact route.

1. Ask for the exact credential and issuer. "CPA, licensed in which state?" and "CTA, member of CIOT?" are fair questions. A named person should hold the credential, not "the team".
2. Check a CPA with the state board. Search NASBA's CPAverify, which is populated with licensing data from participating boards and flags disciplinary actions, or use the licensing state's own board lookup.
3. Check an enrolled agent with the IRS. The IRS lets you verify the status of an enrolled agent through the Office of Enrollment contact form, and its policy is to answer within 72 hours. The IRS Directory of Federal Tax Return Preparers also lists attorneys, CPAs and enrolled agents who hold a valid Preparer Tax Identification Number (PTIN).
4. Check a CTA or ATT with the professional body. Both CIOT and ATT publish member directories on their websites. Search by name and confirm the designation shown matches what the adviser claims.
5. Check HMRC registration and AML supervision. Ask whether the firm has registered as a tax adviser with HMRC or when its window opens, and who supervises it for anti-money laundering purposes.
6. Check the authorisations match. The person named on IRS Form 2848 must be eligible to practise before the IRS, and the UK agent you authorise should be the one actually doing the work.

Illustrative example: A US citizen living in Bristol has used a local UK accountant for years. The accountant is a Chartered Tax Adviser and also prepares her US Form 1040 using a PTIN. The IRS later questions the foreign tax credit on one year's return and proposes additional tax. The accountant can explain the UK figures but, holding no US credential, cannot be named as her representative on Form 2848 for the examination. She now needs a CPA or enrolled agent to take over a return they did not prepare, working from the accountant's UK computations. Had the US return been prepared or reviewed by a US credential holder from the start, the same person could have answered the IRS.

Which credential do you need for your situation?

The credential you need depends on which tax authority is likely to ask questions, and most people with US/UK affairs need both sides covered. As a rough guide:

• An American living in the UK needs a US credential holder for the Form 1040, foreign tax credit and FBAR, and UK tax knowledge for Self Assessment. Our Americans in the UK page describes what that combined work covers.
• Anyone facing an IRS notice, examination or collection issue needs an attorney, CPA or enrolled agent, because only they hold unlimited representation rights. See our IRS representation service.
• Anyone with a UK residence question, split year or remittance issue benefits from advisory-level UK expertise of the kind the CTA examines, plus a registered agent to deal with HMRC.
• Straightforward UK compliance, such as a simple Self Assessment return, is squarely the ground the ATT examines.

Two firms, one per country, can work. Our comparison of one firm or two accountants for US and UK taxes sets out where that arrangement tends to break down, usually in the timing and currency of foreign tax credits.

What people get wrong about tax adviser credentials

Assuming a UK qualification covers the US return

A UK chartered accountant or CTA can be highly skilled and still have no US credential. Preparing a US return needs only a PTIN; representing you if it goes wrong needs a CPA, EA or attorney. Ask the question before the return is filed, not after the IRS writes.

Treating "tax adviser" as a protected title

In the UK, anyone may call themselves a tax adviser. The protection lies in the qualification letters, the professional body membership behind them and, from 2026, HMRC registration. Check all three.

Confusing a PTIN with a credential

A Preparer Tax Identification Number is required for anyone paid to prepare federal returns, but on its own it carries no representation rights. The IRS explains in its credentials guide that PTIN holders without a credential cannot represent clients before the IRS, while Annual Filing Season Program participants have limited rights for returns they prepared and signed.

Checking the firm but not the person

A firm may employ credential holders without the person handling your file being one. Ask who signs the US return, who is named on Form 2848, and who reviews the UK side.

How a cross-border firm combines the credentials

Because no single credential spans both systems, a cross-border practice has to combine them. At firm level, US/UK Cross Border Tax — US CPAs and UK tax advisers working as one team; London, Manchester, New York, San Francisco — is set up so that the US and UK returns are prepared on the same facts and reviewed together. You can read more about how we are organised on our Tax Specialists for US/UK page, and about the UK side of the work on our UK Self Assessment service page.

Whoever you instruct, the test is the same: can you name the credential, the issuer and the person, and can you confirm all three independently? If the answer is yes on both sides of the Atlantic, you have the foundation of a sound engagement. If you would like to talk through your own position, get in touch.