Bitcoin Capital Gains Tax UK: What You Owe in 2025/26

Bitcoin is by far the most widely held cryptocurrency in the UK, and it is the asset most likely to trigger a Capital Gains Tax (CGT) bill. HMRC treats Bitcoin as a capital asset — not a currency — so every time you sell, swap, or spend it you may owe tax on the gain.

Does HMRC know about your Bitcoin?

Increasingly, yes. Major UK-accessible exchanges such as Coinbase, Binance, and Kraken share customer data with HMRC. Under the Crypto-Asset Reporting Framework (CARF), this reporting will become mandatory globally from 2026. Assuming HMRC does not know about your Bitcoin is no longer a safe strategy.

When is Bitcoin subject to CGT?

Any of the following triggers a disposal and a potential CGT event: selling BTC for GBP or another fiat currency, swapping BTC for another cryptocurrency (including stablecoins), spending BTC on goods or services, and gifting BTC to someone other than a spouse or civil partner. Transferring BTC between your own wallets is not a taxable event.

The CGT rates for 2025/26

Basic-rate taxpayers pay 18% on crypto gains. Higher and additional-rate taxpayers pay 24%. Every UK taxpayer has an Annual Exempt Amount of £3,000 — only gains above this threshold are taxable. If your total gains (across all assets, not just crypto) are below £3,000 for the year, you owe nothing.

Calculating your Bitcoin gain

Your gain is the proceeds minus your cost basis. The cost basis is what you originally paid for the BTC, including any trading fees. HMRC requires you to use the Section 104 pool method, which means tracking a weighted average cost across all your BTC purchases rather than identifying specific coins. This gets complicated fast if you have made dozens of purchases over several years.

The same-day and 30-day rules

Before applying the Section 104 pool, HMRC applies two matching rules. If you buy and sell BTC on the same day, those transactions match first. If you sell BTC and buy it back within 30 days, the sale matches against the repurchase (the "bed-and-breakfasting" rule). These rules prevent you from selling to crystallise a loss and immediately repurchasing.

Reporting to HMRC

If your total crypto disposals exceed £12,000 in the year (four times the annual exempt amount), or your net gains exceed £3,000, you must report via Self Assessment. The online deadline is 31 January following the end of the tax year (5 April). Filing late results in automatic penalties starting at £100.

Practical steps

Keep records of every BTC transaction: the date, the amount in BTC, the GBP value at the time, the exchange used, and any fees. If you have been holding BTC across multiple exchanges and years, CryptoLens can import your transaction history and calculate your Section 104 pool automatically.