UK crypto holders: if you swapped one coin for another between 6 April 2025 and 5 April 2026, you may have made a taxable disposal even though no pounds ever reached your bank account. The Self Assessment deadline for that tax year is 31 January 2027. The calculation depends on records only you can put together, so it pays to start well before January.
What counts as a disposal
HMRC's guidance says you may need to pay Capital Gains Tax when you dispose of cryptoassets by:
- selling them;
- exchanging them for a different type of cryptoasset;
- using them to pay for goods or services;
- giving them away (gifts to a spouse, civil partner or charity are treated differently).
The second point catches people out. A coin-to-coin swap on an exchange is a disposal of the token you gave up, even if you never cashed out.
Do you need to report?
HMRC says that if your total gains for the tax year are above the Capital Gains Tax tax-free allowance, you must report them and pay the tax. GOV.UK currently gives the allowance as £3,000 for individuals. You can report through a Self Assessment tax return, which has had its own cryptoasset section from the 2024 to 2025 tax year, completed in pounds sterling, or through HMRC's real time Capital Gains Tax service. For the 2025 to 2026 tax year, online returns and payment are due by 11:59pm on 31 January 2027.
How the gain is worked out
You can't simply subtract what you paid for one purchase from what you got for one sale. HMRC's guidance sets out an order:
- Same day: tokens bought on the same day you sell tokens of the same type are matched first.
- Next 30 days: tokens of the same type bought within 30 days after the sale are matched next.
- The pool: everything else comes from a "pool" for that token type, at the average pooled cost.
Each token type has its own pool, and the pooled cost changes after every acquisition and disposal. That is why a gap in your history affects every later calculation for that token.
Your exchange report is not enough
HMRC says you must keep your own records of your transactions. For each pool it lists the records it expects: the type of token, the date of each disposal, the number disposed of and the number left, the value in pounds sterling, bank statements, and the pooled cost before and after each disposal. An exchange's annual statement may help, but it does not track your pool across other exchanges and wallets.
A simple routine before January
- List every exchange and wallet you used in 2025 to 2026, including dormant ones.
- Download the full transaction history from each, and keep the original files untouched.
- Mark every swap, sale, purchase made with crypto and gift as a disposal to be calculated.
- Record the sterling value of each transaction at the time it happened, and note where that value came from.
- Update a pool for each token type, applying the same-day and 30-day matches first.
- Add up the year's gains and losses and compare the total with the allowance.
- Keep the workings with your return, so you can show how each figure was reached.
If your history includes DeFi, staking, airdrops or transfers between your own wallets, check the specific HMRC guidance for those, or take professional advice.
The guide
The Crypto Tax Reporting & Compliance Guide explains which crypto events are taxable and covers UK Section 104 pooling with the same-day and 30-day rules. Its worksheets include a Cost Basis Tracker and a DeFi Transaction Log for building your own records. It also covers other countries' rules, so use the UK sections and current HMRC guidance for a UK return. Instant PDF.
Sources: GOV.UK: Check if you need to pay tax when you sell cryptoassets; GOV.UK: Capital Gains Tax allowances; GOV.UK: Self Assessment deadlines.
Official guidance checked 2 November 2026. General information, not tax advice.
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