US UK Accountants: Changing Firms Mid Catch-Up Handover
Switching US UK Accountants mid streamlined catch-up? What transfers, what does not, and how the interest clock and October deadlines bite. Talk to us.
Half-built work, changing hands
You can change US UK Accountants midway through a streamlined catch-up, but the work does not simply move with you. Your records transfer; the previous preparer's workpapers may not. Positions already signed and filed are fixed. And every week of handover drift carries a running cost at HMRC's 7.75% late payment interest rate.
Most guidance on changing accountants is written for a business owner switching bookkeepers between quarters. That is not this situation. A multi-year US and UK compliance catch-up is a single, internally consistent evidential package: three years of federal returns, six years of FBARs, a signed non-willfulness certification, and — on the UK side — a linked set of disclosures or late returns that must tell the same story about the same accounts, the same currency conversions and the same reasons for the delay. Handing that over half-built is a specialist exercise, and the failure modes are not administrative. They are evidential.
This guide covers what genuinely transfers between firms, whether an incoming preparer can rely on the outgoing firm's account schedules, which positions are now locked, and how the interest clock and the two October 2026 deadlines compress the window you have to complete the move.
What actually transfers when you change US UK Accountants mid catch-up
The single most common misunderstanding is that "the file" is one thing. It is not. In both jurisdictions the handover splits into three legally distinct categories, and only the first of them is unconditionally yours.
Category one: your records
These are the source documents you provided or that were generated on your behalf — bank and brokerage statements, pension scheme correspondence, ISA valuations, P60s and P11Ds, HMRC references, K-1s, 1099s, closing statements, and copies of any return already filed. In the United States, a practitioner is required to promptly return records necessary for you to comply with your federal tax obligations on request, and an unpaid fee generally does not suspend that duty, although a narrow state-law exception can limit it to the records that must physically attach to a return. In the United Kingdom, the professional bodies require the outgoing firm to respond to a professional clearance letter and to release your books and records; they cannot simply refuse.
Category two: the preparer's workpapers
Lead schedules, FX conversion workings, PFIC computations, foreign tax credit carryover tracking, basis reconstructions, the memo justifying a treaty position, the internal timeline supporting non-willfulness. In most professional frameworks these are the firm's property, not yours. You are entitled to ask; you are frequently not entitled to demand. In practice many firms will release them for a reasonable fee, or will release a redacted subset — but a client who assumes the analytical layer travels automatically is often surprised.
This is the layer that carries the real economic value in a catch-up. Reconstructing eight years of sterling-to-dollar conversions on a portfolio, or rebuilding the cost basis history of an offshore fund holding, can be a substantial share of the total engagement cost. Negotiate for it explicitly, in writing, before you terminate.
Category three: filings and authorisations already in the system
Anything already lodged with the IRS or HMRC does not "transfer" at all — it simply exists. A return filed under the previous firm's PTIN, an FBAR already transmitted, a disclosure already registered: these are now facts on the record that the incoming firm must work around rather than revisit at will.
Agent authority is a separate workstream and should be started the same week you decide to move. Revoking a Form 2848 does not happen automatically when you engage someone new; a stale power of attorney means the outgoing firm continues to receive IRS correspondence, including any notice that lands mid-handover. The mechanics of Form 2848, Form 8821 and HMRC's 64-8 are covered in detail in a separate piece in our guides library, and are outside the scope of this one. Treat authorisation as a parallel task, not a prerequisite — you can begin the substantive handover before it clears.
What transfers: US and UK compared
| Item | United States / IRS position | United Kingdom / HMRC and professional bodies |
|---|---|---|
| Source documents you supplied | Must be promptly returned on request; fee dispute generally no defence | Released under professional clearance; outgoing firm expected to cooperate |
| Copies of returns already filed | Client entitled to copies; preparer retains its own copy | Client entitled to copies of submitted returns and computations |
| Preparer workpapers and schedules | Generally firm property; release is discretionary or chargeable | Generally firm property; clearance letter requests, does not compel |
| Disclosure of your data to the successor firm | Written client consent typically required before the predecessor releases return information | Client authority in the clearance letter provides the release |
| Unpaid fees | Narrow lien possibilities under some state law; federal duty to return core records persists | Lien rules limited; ethical duty to hand over records is not conditional on payment |
| Agent authority | Form 2848 must be affirmatively revoked or superseded | 64-8 or digital agent authorisation replaced; old agent removed |
| Interest running during the gap | Underpayment interest compounds; failure-to-pay additions continue | Late payment interest at 7.75%, repayment interest only 2.75% |
Can the incoming preparer rely on the previous firm's workpapers?
Partially, and the distinction matters more than clients expect. When a new preparer signs a return, that signature is their own representation, made under their own penalties-of-perjury exposure and their own professional standards. There is no mechanism by which the outgoing firm's diligence transfers to the incoming firm. The successor cannot say, in a later examination, that the schedules came from someone else.
What a competent successor can accept
Objective, source-traceable data can generally be adopted after sample verification: opening and closing account balances that tie to statements, dates of transactions, dividend and interest figures agreeing to broker reporting, sterling amounts reported on HMRC documents. If the underlying document is in the file and the schedule ties to it, re-keying it from scratch is waste, not diligence.
What a competent successor re-performs
Anything involving judgement or a chain of assumptions should be re-performed, not inherited. In a US and UK catch-up that typically means:
- Currency conversion methodology. Whether the previous firm used a yearly average, spot rates at transaction date, or HMRC's published rates changes reported income, gains and the foreign tax credit result. The method must also be consistent across all years in the pack.
- The foreign tax credit versus exclusion decision. An exclusion claimed in an early year of the pack constrains later years, and revoking it has consequences that run forward. This is rarely reversible without cost.
- Offshore fund and non-US collective classification. Whether a UK-domiciled fund, investment trust or ISA holding has been treated as a passive foreign investment company, and if so under which regime, is the highest-risk judgement in most cross-border catch-ups.
- Pension treatment and treaty reliance. Whether growth inside a UK scheme has been deferred under the treaty, whether a disclosure position was taken, and whether the same reasoning appears in both jurisdictions' filings.
- The residency and domicile analysis. Statutory residence test conclusions, split-year treatment and any remittance-basis history all feed the UK side and must be consistent with what the US filings assume.
A serious incoming firm will scope this re-performance honestly at the outset rather than discovering it in week six. If you are told that a part-complete pack can simply be picked up and filed, that is a signal to ask more questions, not fewer. Our approach to complex high-net-worth cross-border engagements is to price the verification layer explicitly.
Which positions cannot quietly be changed?
This is the part of a mid-catch-up handover that generalist "how to switch accountants" content never addresses, and it is where clients get hurt.
The non-willfulness narrative
A streamlined submission under the Foreign Offshore Procedure rests on a signed certification of non-willful conduct — negligence, inadvertence, mistake, or a good-faith misunderstanding of the law, as the IRS streamlined filing compliance procedures guidance puts it. That narrative is a statement of facts about what you knew and when. If a draft has already been prepared, discussed in correspondence, or worse, signed and submitted, the incoming firm cannot substitute a materially different account of the same history because it reads better. Two inconsistent narratives about the same facts are discoverable, and inconsistency is precisely the pattern that converts a routine acceptance into an examination.
What a successor can properly do is improve the narrative's completeness, add supporting chronology and documentation, correct genuine factual errors, and remove speculation or legal argument that does not belong in a factual certification. What it cannot do is rewrite your state of mind.
Elections and method choices already made
Where the earliest year of the pack has already been filed, the elections in it are generally binding on the years that follow. Changing the exclusion-versus-credit approach mid-pack, switching a fund's treatment between years without disclosure, or altering an accounting method silently, all produce a package that contradicts itself. The correct route where a prior position is genuinely wrong is a documented correction, not a silent divergence.
Anything already filed outside a formal programme
If the outgoing firm has already filed one or two amended returns or a stray FBAR outside the streamlined framework, that history follows you. The IRS position is that taxpayers who made such filings may still use the streamlined procedures, but penalties already assessed on those filings are not abated. The incoming firm needs to know exactly what went in, when, and under what cover letter, before it designs the remaining pack. Ask for transmittal evidence, not just PDFs.
What does a slow handover actually cost?
Handover delay is not neutral. It has a computable price, and it is asymmetric in the UK.
Per the HMRC interest rates published on gov.uk, late payment interest is 7.75% and repayment interest is 2.75%, both effective from 9 January 2026 on a page last updated 23 December 2025. Late payment interest is set at base rate plus four percentage points; repayment interest at base rate minus one, subject to a floor. The spread means that if a handover stalls while you are simultaneously owed a refund on one year and behind on another, you pay at 7.75% and are compensated at 2.75%. There is no netting benefit in waiting.
On six figures of outstanding UK liability, a three-month handover drift is a four-figure interest cost before any penalty position is considered. On the US side, underpayment interest continues to compound and failure-to-pay additions accrue independently of whether your file is sitting in one firm's queue or another's. Neither authority pauses the clock because you changed adviser.
The practical implication is straightforward: where a liability is already quantified with reasonable confidence, pay it on account during the handover even though the return is not finished. Payment stops interest; submission does not. Many clients get this backwards and hold payment until the pack is complete, which is the most expensive available sequencing.
How the two October 2026 dates constrain the window
Almost every catch-up now running is squeezed by two deadlines that fall ten days apart, in different jurisdictions, with different consequences for missing them.
5 October 2026 — UK registration. If you need to complete a Self Assessment return for the tax year ended 5 April 2026 and you have not filed recently, you must notify HMRC by 5 October 2026, per the gov.uk registration guidance. Telling HMRC after that date exposes you to a failure-to-notify penalty. This is a notification deadline, not a filing deadline — which is exactly why it gets missed during a handover, when both firms assume the other is watching it.
15 October 2026 — US extended filing. The extended due date for individual federal returns. For a client already inside a streamlined pack, the current year return generally sits outside the three-year submission but must not contradict it. Filing a current-year return in October that adopts a different fund classification or a different pension position from the pack you are about to submit creates the inconsistency you were trying to avoid.
Ten days is not enough room to sequence these reactively. In a handover we work backwards from both dates simultaneously: confirm the UK notification position first because it is cheap and absolute, then align the current-year US return to the pack's positions, then submit.
A sequenced handover plan
- Week one. Do not terminate yet. Ask the outgoing firm, in writing, for an inventory: which years are drafted, which are signed, which are filed, and what has physically been sent to any tax authority. Request transmittal evidence.
- Week one to two. Have the incoming firm scope the re-performance layer against that inventory and quote it. Negotiate release of workpapers while the relationship is still intact — leverage disappears the moment you resign.
- Week two. Provide written consent for the predecessor to release your return information to the successor, and start the professional clearance process on the UK side.
- Week two to three. Start authorisation changes in parallel: revoke or supersede the US power of attorney and replace UK agent authority.
- Week three. Quantify and pay any reasonably estimated liability on account in both jurisdictions to stop interest.
- Week four onward. Rebuild the pack for internal consistency across all years and both countries before anything further is submitted. Never mail a partially updated streamlined package.
Where mid-catch-up handovers go wrong
Four patterns recur. First, the client resigns before securing the workpapers, and pays twice for the same analysis. Second, the incoming firm adopts inherited schedules without verification and inherits an error it then signs. Third, the narrative is rewritten to be more flattering, and the file now contains two versions of the taxpayer's own history. Fourth — the most expensive — the pack is submitted in pieces, so the authorities receive an incomplete disclosure that neither firm can now describe as complete and voluntary.
A streamlined submission is designed to be filed as one coherent package. Splitting it across a change of adviser is the structural risk of a mid-engagement handover, and avoiding it is the whole discipline. If you want the full framework for the submission itself, see our work on IRS streamlined filing and on US UK tax accountants.
Taking over a part-complete pack
Jungle Tax regularly takes over catch-up engagements that another firm began. We do it by inventory first, verification second, and submission only when every year in the pack tells the same story in both jurisdictions. We will tell you plainly which parts of the existing work we can adopt, which parts we must re-perform, and what that costs — before you terminate anything.
If your streamlined pack is half-built and stalled, the interest clock and the October dates are both working against you. Contact our cross-border team for a confidential consultation. We will review what exists, tell you what is salvageable, and give you a sequenced route to a clean, consistent submission.
