Sell a UK flat and the clock starts before you have the money

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

You complete on a flat in Bristol. The solicitor sends the money. Nothing else seems to be due.

In fact a clock started on completion day. HMRC wants a 60-day CGT report, plus a payment, long before your tax return is due.

However, nobody in the chain tells you. The estate agent does not. The solicitor often does not either.

Key takeaways

• A 60-day CGT report is due within 60 days of completion.
• Tax is paid then too, not with your January bill.
• Penalties start the day after the deadline passes.
• You file it online, through a separate HMRC account.
• It does not replace Self Assessment, it sits alongside it.
• No gain usually means no 60-day CGT report at all.
• The American return reaches a different number.
• The two countries rarely tax the same figure.

What is the 60-day CGT report?

A standalone return for one sale. You tell HMRC what you sold, what you made, and what tax is due. Per GOV.UK guidance, you file it on its own rather than as part of anything else. Payment goes with it.

Note that it covers UK residential property only.

So it is one sale, one report.

When does the clock start?

On completion, not on exchange. You get 60 days from that date. Exchange can be weeks earlier, so people who count from the wrong day lose most of the window before they begin.

Diarise the date the keys change hands.

In practice sixty days is shorter than it sounds.

Who has to file one?

Anyone who sells UK residential property at a gain that is taxable. A let flat, a second home or an inherited house will all qualify. A main home covered in full by relief usually will not, because no tax is due.

Our guide to selling your UK home as a US citizen covers the relief.

The test is tax due, not profit made.

How do you actually file it?

Through a separate HMRC online service. You set up a property account, get a reference, and enter the figures. It is not inside your normal tax account, which is why people hunt for it and give up.

Set the account up before you need it.

Doing it under time pressure is painful, so start early.

Do you need a Government Gateway login?

Yes, and getting one from abroad is the slow part. Identity checks often want a UK passport, a credit file or a payslip. An American living here for years may have none of those in a usable form.

Start the login weeks before completion.

In fact this single step derails most late filings.

Can an agent file it for you?

They can, once you authorise them on that property account. The authority is specific to it, so your usual tax agent code does not carry across. That extra step surprises people who assume their accountant already has access.

Authorise early, not on day 55.

Because the link takes days, not minutes.

Do you pay at the same time?

Yes. The tax is due with the report, so the money leaves before your return is anywhere near ready. Sellers who have already spent the proceeds find this part genuinely difficult.

Hold back the tax at completion.

So ask the solicitor to ring-fence it.

What if the figure is an estimate?

You may use a reasonable estimate and correct it later. HMRC accepts that costs and reliefs are not always final within 60 days. What it does not accept is a blank return, or a guess with nothing behind it.

Keep a note of how you estimated.

You will need it when you amend.

What if you miss the deadline?

A penalty applies at once, then grows. There is an initial fixed charge, further charges as months pass, and interest on the unpaid tax throughout. None of it depends on HMRC writing to you first.

Our guide to reasonable cause penalty relief covers the American parallel.

File late rather than not at all.

Does it replace Self Assessment?

No, it sits alongside it. The same sale goes on your tax return as well, with the tax already paid treated as a payment on account. Filing one does not excuse the other, which doubles the work on a single disposal.

Our guide to registering for Self Assessment covers the return.

So it is two filings for one sale.

What if there is no tax to pay?

Then usually no report is needed. A sale fully covered by relief, or one inside your annual exempt amount, falls outside the duty. Non-residents are the exception and must report regardless.

Check the exemption before deciding.

Also, the allowance is far smaller than it was.

A worked example

Take an illustrative example. An American in Manchester sells a let flat she bought in 2016.

The gain is £80,000. She files within 60 days and pays £16,800 at the UK higher residential rate of 24% for 2025-26.

Her American return then reports the same sale, but the gain there is larger.

The dollar cost was fixed in 2016 and the pound has moved since. The credit covers most, though not all, of the difference.

Two deadlines, two systems

How does the American return treat the sale?

As a capital gain, worked out in dollars. The cost comes across at the rate on the day you bought, and the proceeds at the rate on the day you sold. Those two rates rarely match, which moves the number.

Our guide to exchange rates on a US return covers the method.

So currency alone can create a gain.

Do the two countries agree on the figure?

Almost never, and you should not expect them to. Different costs are allowable on each side, different reliefs apply, and the whole calculation runs in a different currency. So one sale produces two separate gains, and the foreign tax credit then has to bridge whatever gap is left between them.

Our guide to Form 1116 and the foreign tax credit covers the bridge.

Therefore expect two numbers, not one.

What about main home relief?

Britain is generous and America is not. Britain can relieve a main home in full, while the American exclusion caps it and needs you to have lived there two of the last five years. A long owned family home often clears one test and fails the other.

Our guide to second homes across the two systems covers the overlap.

In short, that gap is where the bill appears.

What about a sterling mortgage?

America can tax the mortgage separately. Repaying a pound loan after the pound has fallen produces a gain in dollars, even though nothing was made in Britain. It is a real charge on a transaction that felt like admin.

Our guide to foreign currency gains on a UK mortgage covers it.

The 60-day CGT report ignores this entirely.

What if you sell at a loss?

No report is due, but the loss is worth claiming. A British loss can shelter later gains once reported, and the American treatment runs on its own rules. Losses go stale if nobody records them.

Our guide to UK capital losses for US citizens covers the claim.

Claim it even if you have nothing to offset yet.

What about jointly owned property?

Each owner files their own. A couple selling together makes two reports, each covering their share. Where one spouse is American and one is not, each side of the sale can attract very different tax.

Our guide to joint accounts for US UK couples covers shared ownership.

So one property can mean two filings.

What about inherited property?

The starting value is usually the value at death. That often means a small gain if you sell soon after, and a large one if you hold for years. The American base cost may differ again.

Our guide to UK inheritance tax meeting the US system covers the estate.

Get a proper valuation at the date of death.

What about a buy to let?

Fully in scope, and the gain is often large. Years of letting means no main home relief, and you have to trace any capital allowances or improvements. Landlords usually have the best records and the biggest bills.

Our guide to UK rental income on a US return covers the letting years.

Depreciation claimed in America matters here.

What if the property sits in a company?

Then the 60-day CGT report does not apply. A company pays corporation tax on the gain instead, through its own return. The American owner then faces the company question rather than a personal gain.

Our guide to running a UK limited company as an American covers that route.

Different wrapper, different rules.

Does it apply if you have left Britain?

Yes, and more strictly. Non-residents must report a disposal of UK property whether or not any tax is due. That catches Americans who moved home and kept a flat behind them.

Our guide to moving back to the US covers the exit year.

No gain still means a report here.

What records do you need?

The purchase and sale completion statements, the cost of improvements, and the dates. Add the exchange rates you used for the American side. Those five things answer almost every later question.

Keep the solicitor's statements from both ends.

However, improvement receipts are the ones people lose.

Can you amend it later?

Yes, and most people do. Final figures arrive after the deadline, so you correct the report once the costs settle. Your tax return then carries the final version of the same sale.

Our guide to overpayment relief for US filers covers reclaims.

Overpaying at first is common and fixable.

What if HMRC asks questions?

They may query the valuation, the costs or the relief claimed. A clear file answers most of it quickly. Problems arise where the gain was estimated and nobody wrote down how.

Our guide to an HMRC enquiry for US filers covers the process.

In our practice good records end it fast.

Does it affect your American deadline?

Not at all. The sale goes on the return for the year it happened, filed on the usual expat timetable. So you may pay Britain in March and report America the following June.

Our guide to US tax deadlines for expats covers the dates.

Two systems, two calendars.

What rate do you actually pay?

Residential property has its own rates, higher than other assets. For 2025-26 the charge is 18% within the basic rate band and 24% above it. Your other income for the year decides where the gain sits, so the same profit can cost two different amounts.

Work out your income before the rate.

For instance, a bonus year pushes more of the gain upwards.

Does the annual exempt amount still help?

Barely. The allowance has been cut hard in recent years and now shelters only a few thousand pounds of gain. On a property sale it rarely changes whether a 60-day CGT report is needed, though it still trims the bill slightly.

It is worth claiming and no longer worth planning around.

But couples each get their own.

What if you lived in it for part of the time?

Then you apportion relief across your ownership. The years it was your only home are covered, the let years are not, and a final period of ownership is usually added back in your favour. The arithmetic is simple once the dates are right.

Write down the dates you moved in and out.

Because those dates drive the whole calculation.

What if you sell to a family member?

HMRC ignores the price you agree. HMRC treats a sale to a connected person as happening at market value, so selling cheaply to a child does not reduce the gain. The 60-day CGT report has to use that market figure instead.

Get a valuation before agreeing anything.

America applies its own gift rules as well.

What if the sale falls through and completes later?

The clock follows the completion that actually happens. A collapsed chain resets nothing, because no disposal took place. Where a sale completes months after exchange, the sixty days still run from the later date rather than from the contract.

So only completion matters for the deadline.

Keep the final statement as proof of the date.

Does it apply to land or commercial property?

Not usually. The duty covers UK residential property, so an office, a shop or bare land falls outside it for a resident seller. The gain still goes on your tax return in the normal way, just without the separate sixty day filing.

Mixed use buildings need splitting.

For example, a flat above a shop is the common case.

How to file the 60-day CGT report

1. Note the completion date and count 60 days from it.
2. Set up the HMRC property account and a Government Gateway login.
3. Authorise your agent on that account if one is acting.
4. Gather both completion statements and any improvement costs.
5. Work out the gain, using a reasonable estimate if costs are unsettled.
6. File the 60-day CGT report and pay the tax together.
7. Put the same sale on your Self Assessment return later.
8. Convert everything to dollars separately for the American return.

Mistakes and penalties we see with the 60-day CGT report

The first is counting from exchange instead of completion, which loses weeks.

The second is leaving the Government Gateway login until the last fortnight.

The third is spending the proceeds before the tax has been set aside.

The fourth is assuming the UK figure can simply be copied onto the American return.

How US UK Tax Accountants helps

We work out both gains before completion where we can, so you hold the money back and nobody meets a surprise by a bill in week eight.

Then we file the report and carry the same sale through to the American return. Our property gains service covers both sides.

If you have sold, or are about to, get in touch before the 60 days run down.

Last reviewed 21 October 2026. This article is general information and not personal tax advice, and rates and allowances change each year.