The refund arrives four years late and takes your American credit with it

Figures relate to tax year 2025-26 (UK) · 2025 (US)

Most people find an overpayment by accident. A new accountant spots a relief nobody claimed, or a coding error that ran for three years, or an expense that should have come off the profit and never did.

Reclaiming it from HMRC is a defined process with a hard deadline. That part is manageable. The part that catches Americans is what happens on the other side, because the British tax you are about to get back is tax you already claimed as a credit on an American return.

Overpayment relief therefore has a second step that nobody mentions in the British guidance. Get the money back here and your American figures for that year stop being correct.

Key takeaways

• Overpayment relief reclaims tax you should never have paid.
• The deadline is four years from the end of the tax year.
• It only applies where no other route to a refund exists.
• HMRC refuses claims in several defined circumstances.
• A British refund reduces the foreign tax credit you already claimed.
• You generally have to amend the American return for that year.
• The American amendment window can close before the British one.

What is overpayment relief?

It is the route to reclaim tax you paid but did not owe, where no other mechanism applies. According to HMRC guidance, it covers both tax paid under a mistake in a return and tax assessed on a basis that was never right.

It exists because the ordinary amendment window is short. You can amend a self assessment return for twelve months after the filing deadline. After that the return closes to you, even where it is plainly wrong.

Overpayment relief reaches further back than that window. It is the safety valve for errors found late, and most errors surface late.

What is the deadline?

Overpayment relief runs out four years from the end of the tax year concerned. For the year ended 5 April 2022, the claim had to reach HMRC by 5 April 2026, and a day late is simply out of time with no discretion available.

That deadline is absolute. HMRC cannot extend it, a reasonable excuse does not help, and the fact that you only discovered the error last week makes no difference to the outcome.

So the first thing to establish on any historic error is which years are still open. There is no point building a case for a year that closed in April.

How do you make a claim?

In writing, and it must contain several specific things. The claim must state that it is a claim for overpayment relief, identify the tax year, quantify the amount, explain why the tax was not due and include a signed declaration that the details are correct.

Missing any of those elements can invalidate the claim entirely. A letter that merely asks for a refund and explains the circumstances is not a claim, and HMRC can reject it as defective rather than treat it as a first attempt.

Where the deadline is close, the defect matters enormously. A rejected claim resubmitted after the four year point is out of time, even though the original letter arrived in good order.

A worked example

The figures below are illustrative. They use round numbers so you can follow each step and substitute your own.

Michael is American and lives in Bristol. In 2026 his new accountant finds that pension contributions were never claimed on his 2022-23 return, and that the error cost him £6,000 of British tax.

He makes a valid overpayment relief claim in time and HMRC refunds the £6,000 with repayment interest. On the British side that is the end of the matter.

His American return for 2022 claimed a foreign tax credit based on British tax of £24,000. The real figure was £18,000. His credit was therefore £6,000 too high, which understated his American tax for that year.

He now has to amend the 2022 American return and pay the difference with interest. The refund was still worth having, because British rates exceed American ones here, but the net gain is smaller than the cheque suggests.

Why does a refund reduce your credit?

Because the credit relieves foreign tax you actually paid and kept. Getting the tax back means you did not ultimately bear it, so the credit claimed on that basis was too large and the American return no longer reflects reality.

America expects you to tell it when a foreign tax changes. A drop in foreign tax paid is a specific event. It requires you to correct the return rather than wait for the next filing.

Our guide to amending a US return covers the mechanics. Amend the year you originally claimed the credit, not the year the refund arrived.

The two timetables compared

The table shows why these claims need planning. The windows are different lengths and they start at different points.

Is there enough time on the American side?

Usually yes, because the window for adjusting a foreign tax credit runs longer than the ordinary one. America allows ten years from the due date of the return for a claim connected to foreign taxes, which comfortably covers a four year British claim.

That length cuts both ways. A longer window to claim a refund is also a longer window for America to collect where a credit turns out to have been too generous.

So the extended period is not a reason to delay. It simply means the correction is still possible when the British refund eventually lands.

When will HMRC refuse a claim?

In several defined situations, and the list is longer than people expect. The main one covers a view of the law that everybody accepted at the time, which a later case then changed.

HMRC also refuses where another remedy was available and you did not use it. Letting the ordinary amendment window lapse and then reaching for overpayment relief does not work if you could simply have amended in time.

These exclusions stop overpayment relief becoming a general right to reopen settled years.

What if the mistake was HMRC's?

The same four year deadline applies, which strikes most people as unfair. A wrong tax code operated for three years is still your claim to make, and still subject to the same limit as an error you made yourself.

There is a separate concession for official error in limited circumstances, but it is narrow and rarely the answer. The practical response is to check your coding notices rather than rely on recovering the money later.

Our guide to an HMRC enquiry covers the position when the correction runs the other way.

Does repayment interest complicate things?

A little, because the interest is itself taxable income in both countries. HMRC adds repayment interest to a refund, and that interest is not a reduction of tax but a separate receipt to report.

The amounts are usually small against the refund itself. They still belong on the American return for the year you received them. That is a different year from the one you are correcting.

So a single claim can touch three tax years: the year of the error, the year of the amendment, and the year the interest arrives.

What if you no longer live in Britain?

You can still claim, and leaving does not shorten the four year window. The practical obstacle is usually a closed British bank account, since HMRC prefers to repay into one and an overseas transfer takes longer to arrange.

Keep one British account open while any claim is outstanding. It is the single most common cause of delay we see on these refunds.

Your American filing obligation follows you wherever you live, so a move changes nothing on the amendment side.

Is a claim always worth making?

Not always, and overpayment relief is worth modelling before you spend money on it. Where British rates exceed American ones, a refund usually leaves you ahead even after the American adjustment, because you only lose credit you were not using anyway.

The calculation changes if you were in excess credit for that year. Then the extra British tax was buying you nothing, and reclaiming it is pure gain with no American cost at all.

It can also go the other way. Where the credit absorbed everything, each pound refunded here costs you something there. A small claim may not survive the fees.

Can you claim overpayment relief for several years at once?

You can, and you usually should where the same error ran across them. Each year needs its own claim with its own figures, but you can send them together and HMRC will normally deal with the set as one piece of work.

Watch the oldest year closely. It is the one nearest the deadline, and a defect that sends the whole bundle back can push it out of time while the later years survive.

Submit the oldest year first if time is short. Do not let it wait for the others to be ready.

What if HMRC rejects the claim?

You can ask for a review and then appeal to the tribunal, on the same timetable as any other decision. The window is usually thirty days from the rejection, which is short when the underlying claim took months to prepare.

A rejection on technical grounds is worth challenging where the substance is sound. A rejection because another remedy existed rarely is, since that exclusion is clear in the legislation.

Either way, do not resubmit a corrected claim after the four year point and hope. It will be out of time whatever the merits.

Does it work for National Insurance too?

Overpaid National Insurance runs on its own track with its own rules, so an overpayment relief claim does not cover it. The usual route is a separate refund application to HMRC quoting the contribution years involved.

This matters for anyone who paid into both systems before a certificate of coverage was in place. Contributions paid in the wrong country are recoverable, though the process is slow.

Our guide to the certificate of coverage covers how to stop it happening again.

What about a company rather than an individual?

Corporation tax has its own overpayment route with a similar four year limit, measured from the end of the accounting period. The principle is the same and the forms are different.

For an American owner the knock-on is different too. Corporation tax usually feeds a credit at company level rather than on your personal return, so the American consequence depends on the structure.

Our guide to Form 5471 categories covers the reporting that sits around it.

What records do you need?

The original return for the year, the evidence showing what the correct figure should have been, and a copy of the American return that claimed the credit. Those three let you quantify both sides before committing to a claim.

Keep the HMRC repayment notice as well once it arrives. It shows the tax refunded and the interest separately, which is exactly the split the American amendment needs.

Without that notice you are reconstructing the figures from a bank credit, and the interest element is invisible in a single lump sum.

How to handle a claim

1. Identify which tax years are still inside the four year window.
2. Quantify the overpayment and gather the supporting evidence.
3. Check whether another remedy was available at the time.
4. Pull the American return that claimed the credit for that year.
5. Model whether the refund leaves you better off after the adjustment.
6. Submit a claim containing all the required formal elements.
7. Amend the American return once the refund is agreed.
8. Report the repayment interest in the year you receive it.

Mistakes and penalties we see with overpayment relief

The first is reclaiming British tax and never revisiting the American return. That leaves an overstated credit on a filed return. It understates American tax rather than leaving a harmless loose end.

The second is sending a letter that does not meet the formal requirements. It reads like a claim, HMRC rejects it as defective, and the replacement arrives out of time.

The third is amending the wrong American year. The correction belongs in the year you claimed the credit, not the year the money came back.

The fourth is forgetting the repayment interest altogether. It is small, it is taxable, and it sits in a different year from everything else in the claim.

How US UK Tax Accountants helps

We check which years remain open, quantify the British claim properly, and model the American consequence before you submit anything. Where the net position is negative we say so rather than claiming for the sake of it.

Where a refund already arrived and nobody amended anything, we work out what remains open and what it costs to put right. Our US federal return service covers the filing.

If you think you have overpaid British tax in an earlier year, get in touch. Nothing fixes the four year deadline once it passes.

Last reviewed 9 October 2026. This article is general information and not personal tax advice. Every claim turns on its own facts, so take advice on yours before submitting.