Switching US-UK tax accountant is a records exercise more than a paperwork one. You do not need your old firm's permission, and neither the IRS nor HMRC needs to approve the change. What you do need is the carried-forward data only your old adviser holds: foreign tax credit carryovers, PFIC and pension basis, depreciation schedules and treaty elections. Collect those first, then sign new authorisations with each tax authority.
People change advisers for good reasons: missed deadlines, a firm that handles only one country, fees that grew without explanation, or a new situation such as a UK company. In our experience, switching US-UK tax accountant is easy in itself. The damage comes later, when a new preparer has to rebuild numbers nobody handed over. This guide sets out what to request, how the authorisations work in each country, and the best time of year to move.
What to collect before switching US-UK tax accountant
A tax return is the visible output of a much larger working file. Several figures roll forward from year to year and cannot be reconstructed from the return alone.
The US carry-forward items
Ask for full copies of at least the last three years of US returns, including every form and statement, not just Form 1040. Then ask specifically for the supporting schedules. These include foreign tax credit carryovers by category from Form 1116 Schedule B, passive foreign investment company elections and basis from Form 8621, depreciation schedules for any rental property, capital loss and net operating loss carryovers, and your US basis in UK pensions.
The UK and company items
On the UK side, request your Self Assessment returns and tax calculations, capital loss records and any claims in force, such as the foreign income and gains regime. If you own a UK company, request the Form 5471 history, earnings and profits calculations and any section 962 election workings. Our guide to Form 5471 categories of filers shows why that history matters.
| Record | Why the new adviser needs it | Can it be rebuilt without the old firm? |
|---|---|---|
| Filed returns, last 3 to 6 years | Baseline for every later year | Partly, from IRS transcripts and HMRC online |
| Foreign tax credit carryovers by category | Unused credits last ten years | Only by recomputing each year |
| PFIC elections and basis | Determines tax on every future sale | Difficult and costly |
| Pension basis and treaty positions | Decides how distributions are taxed | Difficult |
| Depreciation schedules | Needed annually and on sale | Yes, with purchase records |
| Form 8833 treaty disclosures | Positions must stay consistent | Yes, from filed returns |
Your right to your records
In the US, practitioners who represent clients before the IRS are governed by Treasury Department Circular 230. Section 10.28 requires a practitioner to return, at the client's request, the records the client needs to meet their federal tax obligations. A fee dispute does not generally remove that duty for the client's own records. The IRS publishes the rules on its Circular 230 page. In the UK, members of professional bodies follow similar handover expectations through professional clearance letters.
If the old firm is slow
You are not stuck. You can obtain IRS account and return transcripts yourself through an IRS online account or with Form 4506-T. HMRC lets you view and download filed Self Assessment returns from your personal tax account. These do not replace working papers, but they give the new adviser a verified starting point.
Authorising the new adviser
Each tax authority has its own authorisation, and the old one does not lapse automatically in every case.
IRS: Form 2848 and Form 8821
Form 2848, Power of Attorney and Declaration of Representative, lets an enrolled agent, CPA or attorney represent you before the IRS. Form 8821, Tax Information Authorization, only lets someone receive your information. Filing a new Form 2848 for the same tax matters and years generally revokes the earlier one, unless you tick the box to retain it. Our guide to the Enrolled Agent, CPA and Chartered Accountant credentials explains who can sign.
HMRC: agent authorisation
In the UK, your new agent requests access through HMRC's online agent services, and you approve it, or you complete form 64-8. You should also remove the old agent in your HMRC online account. HMRC explains the process in its guidance on appointing someone to deal with HMRC for you.
When to time switching US-UK tax accountant
Timing matters because US and UK deadlines do not align. The UK tax year ends on 5 April, with Self Assessment due on 31 January. The US return is due on 15 April, or 15 June for Americans abroad, and can be extended to 15 October. Therefore, the cleanest window is usually late autumn, after both the US extended deadline and before the UK January rush. Avoid switching mid-return if you can.
One firm or two?
Many Americans in Britain use one adviser for each country. That works only if the two actually talk to each other. A foreign tax credit depends on UK tax figures, and a UK claim can depend on US tax paid. A single dual-qualified team removes that gap, as our cross-border taxation page explains. Our list of questions to ask a US-UK tax adviser helps you test a new firm before you commit.
An illustrative case
Consider an illustrative American in Bath who moved from a US-only preparer to a dual-qualified firm in November 2026. The facts are illustrative. Her old preparer supplied the returns but no Form 1116 workings. Her new adviser recomputed four years of general category carryovers and found unused credits that had never been tracked. Those credits later reduced US tax in a year when she received a US bonus. Without the review, they would have expired unused.
If you are thinking about switching US-UK tax accountant, book a consultation with our team. We request your records, review the last three years and take over both countries' filings.
Frequently Asked Questions
Can I change my US tax accountant at any time?
Yes. You can change adviser at any point and do not need your old firm's consent or approval from the IRS or HMRC. The practical question is timing, because switching in the middle of a return risks duplicated work and missed deadlines.
What records should I get when switching US-UK tax accountant?
Request full copies of your US and UK returns for at least three years, plus the working schedules behind them: foreign tax credit carryovers by category, PFIC elections and basis, pension basis, depreciation schedules, loss carryovers and any Form 8833 treaty disclosures.
Does my old accountant have to give me my records?
In the US, Circular 230 section 10.28 requires a practitioner to return the client records needed to comply with federal tax obligations when the client asks. You can also obtain IRS transcripts and HMRC return copies yourself.
Do I need a new Form 2848 for my new US tax adviser?
Yes, if you want them to represent you before the IRS. A new Form 2848 covering the same tax matters and years generally revokes the earlier power of attorney unless you choose to retain it. Form 8821 only authorises someone to receive your tax information.
How do I change my tax agent with HMRC?
Your new agent requests authorisation through HMRC's online agent services and you approve it, or you submit form 64-8. You should also remove the previous agent's access in your HMRC online account.
When is the best time to switch tax accountant as an American in the UK?
Late autumn is usually best. It falls after the US extended filing deadline of 15 October and before the UK Self Assessment deadline of 31 January, so neither country's return is mid-preparation.
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