Explainerone question answered

When do you pay capital gains tax

Fahad ZarCrypto tax accountant. MSc Accounting and Finance, BPP University London. Four years reconciling wallet and exchange histories for UK and US filings.

Published 25 August 2026· Reviewed against gov.uk 25 August 2026· 4 min read·Capital gains tax

There is no bill. That is the part that catches people. Capital gains tax never arrives as an invoice, you work out whether your gains beat the £3,000 allowance and then one of three clocks applies, per GOV.UK. Which clock depends on what you sold.

Property answers to a 60 day clock and everything else answers to 31 January. Knowing which clock you are on is the entire game.

Property, 60 days from completion

Sell a UK residential property that is not covered by main home relief and you have 60 days from completion to report the gain and pay the tax, through HMRC’s property reporting service. This has applied to completions since 27 October 2021, and for the window between April 2020 and that date the limit was 30 days. The clock runs from completion, not exchange, and it does not wait for your accountant to be free.

GOV.UK is blunt about the consequence, waiting for the next tax return instead brings interest and a possible penalty. Non-residents have it stricter still, they must report every sale of UK property, residential or not, even when no tax is due.

Everything else, Self Assessment and 31 January

Shares, crypto, business assets and everything outside residential property go through Self Assessment. The gain is reported in the return for the tax year of the disposal, and the tax is due with that return, by 31 January after the tax year ends. A disposal on 10 April 2026 sits in the 2026 to 2027 tax year, so its tax is due 31 January 2028. A disposal a week earlier fell in 2025 to 2026 and is due 31 January 2027. Two sales days apart, tax dates a year apart.

That edge is usable. Realising a gain just after 5 April buys nearly two years of cash flow, which is one of the few pieces of timing planning HMRC has no quarrel with. If the disposal means your first ever return, registration has its own deadline, 5 October after the tax year.

The middle route, real time reporting

If you would rather not carry the liability, the real time CGT service takes reports of non-property gains as they happen, up to 31 December in the tax year after the sale. It suits people with a single disposal who do not otherwise file. If you are in Self Assessment anyway, it saves nothing, the return still has to include the gain.

Where crypto fits

Crypto follows the Self Assessment clock, but with one practical difference, the disposal date is every swap, sale and spend through the year, not one completion date you would remember. The tax date is set by the tax year those disposals fell in, and by the time January arrives the reconstruction is the slow part. The full deadline calendar sets out the year, and every disposal inside it counts individually, as the gains guide explains.