Most crypto tax numbers are wrong because the matching rules are skipped. UK capital gains on cryptoassets are not simply proceeds minus what you paid. Every disposal is matched against acquisitions in a strict statutory order: same day first, then anything bought in the following 30 days, then the section 104 pool. Apply them in the wrong order, or not at all, and the answer can be out by thousands of pounds in either direction.
This calculator applies the order correctly. It runs entirely in your browser, nothing is uploaded or stored, and it handles multiple tokens, part disposals and crypto-to-crypto swaps.
| Token | Date | Type | Quantity | Value £ | Fees £ |
|---|
Enter every acquisition and disposal of each token, including crypto-to-crypto swaps valued in sterling on the day. Value is the sterling consideration excluding fees. Nothing you type leaves your browser.
How to use it
- One row per transaction. Enter the token ticker, the date, whether it was an acquisition or a disposal, the quantity and the sterling value.
- Value crypto-to-crypto swaps in sterling. A token-for-token exchange is two entries: a disposal of what you gave up and an acquisition of what you received, both at the sterling market value on the day.
- Include fees separately. Fees on acquiring are added to cost; fees on disposing are deducted from proceeds. Fiat deposit and withdrawal fees are not allowable and should be left out.
- Do not enter transfers between your own wallets. Moving tokens between addresses you beneficially control is not a disposal. Entering them is the single most common cause of a wildly overstated gain.
- Enter the full history for each token, not just the current tax year. The pool is cumulative, so a purchase from 2017 still affects a disposal made today.
The three matching rules it applies
- Same-day rule (s.105 TCGA 1992). Tokens of the same type acquired on the day of disposal are matched first.
- The 30-day rule (s.106A TCGA 1992). Acquisitions in the 30 days after a disposal are matched next, earliest first. This is the bed and breakfast rule, and it is mechanical: it applies whether or not you intended it.
- Section 104 pool. Everything else is matched against a single averaged pool per token type, held across all your wallets and exchanges. Pooling is by token, not by location.
NFTs are excluded from pooling entirely, because each one is separately identifiable. Do not enter them here; see our NFT and airdrop tax page instead.
What the 30-day rule does to a simple trade
Press Load example above to see it. Two bitcoin bought in January 2024 for £60,000 and one in March 2025 for £45,000 gives a pool of 3 BTC at £105,000, an average of £35,000 each. Sell 1 BTC in June 2026 for £70,000 and the intuitive answer is a gain of £35,000.
It is not. Buying 0.5 BTC eight days later for £34,000 drags half the disposal out of the pool and matches it against that later, far more expensive purchase. Half the sale is matched at £34,000 of cost against £35,000 of proceeds, a gain of £1,000. The other half comes from the pool at £17,500 against £35,000, a gain of £17,500. The correct total is £18,500, and the pool afterwards holds 2.5 BTC at £87,500 rather than 2.5 BTC at £87,500 plus the coins you thought you had added.
A naive averaging calculation gives £35,000. The rules give £18,500. Full detail, with the statutory references, is on our section 104 pooling page.
Rates, allowances and reporting for 2026/27
- Annual exempt amount: £3,000 for individuals.
- Rates: 18% to the extent gains fall within your unused basic rate band, 24% above it.
- Reporting: you must report through Self Assessment if total disposal proceeds exceed £50,000, or if your net gains exceed the annual exempt amount. The proceeds test applies even if you made no gain at all.
- Losses: set against gains of the same year first; unused losses can be carried forward, but only if claimed, generally within four years of the end of the tax year of the loss.
What this calculator does not do
It is a capital gains tool, deliberately scoped. It does not compute income tax on staking rewards, mining income, airdrops received for a service or DeFi returns, all of which are taxed as income on receipt and then acquire a base cost for a later disposal. It does not carry losses forward between years, model negligible value claims for stolen or worthless tokens, handle NFTs, or decide whether your activity amounts to a trade rather than investment. Nor does it reconstruct missing history from a dead exchange, which is the part most people actually need: that is transaction analysis and reconciliation.
Treat the output as a well-founded estimate, not a filed figure.
Frequently asked questions
Is this crypto tax calculator free?
Yes, and there is nothing to sign up for. It runs entirely in your browser using JavaScript. No transaction data is transmitted to us or to anyone else, and nothing is saved when you close the page.
How is crypto capital gains tax calculated in the UK?
Each disposal is matched against acquisitions in a fixed statutory order: same-day acquisitions first, then acquisitions in the following 30 days, then the section 104 pool, which holds an averaged cost for all remaining tokens of that type. The gain is proceeds less the matched allowable cost. For 2026/27 the annual exempt amount is £3,000 and the rates are 18% and 24%.
Is swapping one coin for another taxable?
Yes. Exchanging one token for a different type of token is a disposal of the first, at its sterling market value on the day, and an acquisition of the second at the same value. You never touched cash, and you can still have a substantial tax liability. Enter each swap as two rows.
Do I need to enter transfers between my own wallets?
No, and you should not. Moving tokens between addresses you beneficially control is not a disposal. Entering them is the most common reason a portfolio tracker reports a gain many times larger than the real one, because unlabelled internal transfers are read as sales.
Does the 30-day rule apply if I did not mean to bed and breakfast?
Yes. It is entirely mechanical. Any acquisition of the same token within 30 days after a disposal is matched against that disposal regardless of intention, including automated buys, dollar-cost averaging and rebalancing.
Do I have to report if I made a loss?
Possibly. The £50,000 disposal-proceeds test is independent of whether you made a gain, so high-volume trading can trigger a filing requirement with no tax to pay. Separately, capital losses are worth reporting because they must be claimed to be carried forward against future gains.
Can I use different pools for coins on different exchanges?
No. Pooling is by token type, not by location. All your bitcoin sits in one section 104 pool whether it is on Coinbase, on Kraken, in a Ledger or in a hot wallet. This is one of the biggest differences between the UK and the United States, which tracks basis wallet by wallet.
My software gives a different number. Which is right?
It depends on what the software was told. The usual culprits are unlabelled internal transfers, missing cost basis from a delisted exchange, a wrong sterling valuation on a swap, or a tool applying the US or a generic FIFO method rather than UK pooling. We reconcile these routinely, and the corrected figure is more often lower than higher.
Will you check my figures before I file?
Yes. We prepare and file crypto capital gains computations as part of Self Assessment, and we review computations prepared by others. Send us the export and we will tell you where it diverges from the statutory treatment before it goes to HMRC rather than after.
This calculator and page are general guidance on UK tax law as at 10 August 2026 and are not advice for any particular case. Output is an estimate and should not be filed without review. HMRC's internal manuals, including the Cryptoassets Manual, are guidance for HMRC staff, are not law, and do not bind HMRC in an individual case. Reviewed by the TaxDigit crypto tax team. Updated August 2026.
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