How Londoners Declare Crypto Profits to HMRC (2026)
You bought some Bitcoin in 2023, watched it climb, sold a chunk last year to fund a holiday — and now a letter-shaped anxiety has settled in: does HMRC know, and were you supposed to tell them? You’re not alone. Hundreds of thousands of Londoners now hold crypto, and surveys consistently show most have no idea how UK tax applies to it. Here’s the reassuring part: declaring crypto profits to HMRC is straightforward once you understand the rules, and for most people with modest gains it takes less than an hour.
This guide covers exactly what counts as a taxable crypto event, how Capital Gains Tax works on crypto in 2026, how to calculate what you owe, how to report it through Self Assessment, and the record-keeping habits that make the whole thing painless.
What HMRC actually taxes (and what it doesn’t)
HMRC treats cryptoassets as property, not money. That single classification drives everything. You don’t pay tax for buying crypto, holding it, or transferring it between your own wallets. Tax events happen on disposal: selling crypto for pounds, swapping one crypto for another (trading Bitcoin for Ethereum counts), spending crypto on goods or services, or gifting it to someone other than your spouse or civil partner.
Each disposal is assessed for Capital Gains Tax: sale value minus purchase cost (plus allowable costs like exchange fees) equals your gain. Add up your gains across the tax year, subtract the annual exempt amount — £3,000 in 2026/27 — and CGT applies to the remainder. Note how far that allowance has fallen: it was £12,300 just a few years ago, so far more ordinary investors now have taxable gains than realise it.
Two things people miss: swapping crypto for crypto is taxable even though no pounds changed hands, and HMRC’s official crypto tax guidance confirms that “I never cashed out” is not a defence. If you traded ETH for a meme coin at a profit, that profit is taxable.
How the maths works: a worked example
Let’s make it concrete. In March 2024 you bought 0.5 BTC for £25,000 (including fees). In November 2025 you sold 0.2 BTC for £16,000. Your cost basis for the 0.2 BTC is proportional: 0.2/0.5 × £25,000 = £10,000. Your gain is £16,000 − £10,000 = £6,000.
Subtract the £3,000 annual exempt amount: £3,000 of taxable gain remains. The CGT rate depends on your income: basic-rate taxpayers pay 10% on gains within their remaining basic-rate band (so £300), while higher and additional-rate taxpayers pay 24% (£720). If your gains push you across the threshold, you pay 10% on the slice within the basic-rate band and 24% above it.
Real portfolios are messier — dozens of trades, staking rewards, airdrops — which is why crypto tax software (Koinly, CoinTracking and similar) exists. These tools connect to exchanges via read-only API keys, import your history, apply HMRC’s pooling rules, and generate a tax report. For anyone with more than a handful of transactions, they’re worth every penny of their £50–£150 annual cost.
When crypto counts as income instead
Not everything is Capital Gains Tax. If you receive crypto as payment for work, from mining, or as staking rewards, HMRC generally treats it as income — subject to Income Tax (and potentially National Insurance) at the pound value when received. When you later sell that crypto, CGT applies to any further gain above that value.
This catches out more people than you’d think: the freelancer paid in stablecoins, the hobbyist miner, anyone earning staking yields. If you’re registered as self-employed with HMRC, crypto income goes on the same return. And if you’re unsure whether your activity counts as trading (Income Tax) or investing (CGT), that’s precisely when getting an accountant’s advice pays for itself — the boundary is genuinely murky.
How to report: Self Assessment step by step
Most people report crypto through Self Assessment. If you don’t already file a return, register for Self Assessment by 5 October following the tax year in which you made the gains. The return itself is filed online by 31 January, with payment due the same day.
In the return, crypto gains go in the Capital Gains section. You’ll need: the type of cryptoasset, disposal dates, sale values in pounds, purchase costs, and allowable expenses. HMRC’s pooling rules (the “Section 104 pool”) mean you generally average your costs across holdings of the same asset rather than matching specific buys to sells — tax software handles this automatically, but if you’re doing it manually, the guidance walks through the method.
If your total gains are below the £3,000 allowance and your total disposals below £50,000, you typically don’t need to report at all — but keep records anyway. Allowances change, and HMRC can ask questions going back years. Freelancers already used to tracking income will find the discipline familiar; our overview of how much tax UK freelancers pay covers the broader Self Assessment landscape.
Record-keeping: the habit that saves you
The single biggest favour you can do your future self is to log every crypto transaction as it happens: date, type (buy/sell/swap/transfer/gift), amounts, pound values, fees, and wallet addresses. A spreadsheet works; tax software works better. Reconstructing three years of exchange history under a January deadline is miserable — exchanges delist, APIs break, and CSV exports go missing.
Keep records for at least six years after the tax year, which is HMRC’s standard window. And remember: transferring between your own wallets isn’t taxable, but you still want the trail documented, because an unexplained on-chain movement looks identical to a disposal until you prove otherwise.
Conclusion
Declaring crypto profits to HMRC comes down to four steps: know what counts as a disposal (sales, swaps, spending, gifts), calculate gains minus the £3,000 annual allowance, report through Self Assessment by 31 January, and keep records of everything. For modest gains the process is genuinely simple; for active traders, tax software plus an accountant is money well spent. The penalties for ignoring it — interest, fines, and in serious cases criminal investigation — dwarf the cost of compliance. Crypto’s promise was freedom from banks, not from the taxman. Declare it, pay what’s due, and sleep well.
Frequently Asked Questions
Do I need to declare crypto if I made less than £3,000 profit?
Usually not, provided your total disposals were also under £50,000 — gains within the annual exempt amount aren’t taxable. But keep full records anyway, since allowances and circumstances change.
Is swapping Bitcoin for Ethereum a taxable event?
Yes. HMRC treats crypto-to-crypto swaps as disposals, taxable on the gain at the time of the swap — even though no pounds changed hands. This is the most commonly missed tax trigger.
What if I lost money on crypto?
Capital losses can be reported and carried forward to offset future gains, reducing future tax bills. You must report the losses to HMRC within four years to claim them — losses don’t offset automatically.
Do I pay tax on crypto given as a gift?
Gifting crypto to anyone other than your spouse or civil partner is a disposal at market value — CGT may apply. Gifts between spouses are tax-free at the time of transfer.
What happens if I don’t declare my crypto gains?
HMRC receives data from UK exchanges and uses blockchain analytics. Non-declaration risks penalties, interest on unpaid tax, and investigation. Voluntary disclosure before you’re caught always leads to lighter treatment.