Crypto Tax Calculator UK 2026: how to calculate CGT step by step

Calculating UK crypto tax for 2026 means turning every sale, swap and gift into a pound-denominated gain or loss, matching disposals against your Section 104 pool, then applying the £3,000 Annual Exempt Amount before paying 18% or 24% CGT. This guide walks through the five-step HMRC method and shows you the three tools that automate it.

How do I calculate UK crypto tax?

The five-step framework below mirrors the order HMRC uses in its Cryptoassets Manual. Work through it once on a spreadsheet for a single coin and the rest of your portfolio becomes mechanical. If your portfolio runs to more than fifty disposals a year, jump to the UK crypto tax guide for the full background, then automate the calculation with a tool.

Two notes before starting. First, HMRC treats individuals as investors by default — your gains fall under Capital Gains Tax, not income tax. Only a tiny minority of UK taxpayers will ever be reclassed as financial traders, and meeting the test requires sustained, organised, business-like activity. Second, all calculations are in pounds. Every USD price has to be converted at the rate on the transaction date, not at year-end.

Step 1: Gather every disposal

A disposal is any transaction where you give up beneficial ownership of a cryptoasset. HMRC counts five categories and they all crystallise a gain or loss in 2026:

• Selling for fiat — GBP, EUR, USD or any other currency.
• Swapping one token for another — BTC to ETH, stablecoin to altcoin, wrapped to native.
• Spending crypto on goods or services — paying for a coffee with USDC counts.
• Gifting to anyone other than your spouse or civil partner — market-value disposal.
• Donating to a non-registered charity — only gift-aid-eligible charities sidestep CGT.

Pull a CSV from every exchange and wallet you used in the tax year. Each row needs a date, the asset, the number of units disposed of, the proceeds in GBP at the disposal date and any allowable fees. For on-chain transactions, use the block timestamp and the Bank of England daily spot rate, or the exchange-quoted GBP rate at the moment of the trade. Keep the source data: HMRC expects records for five full years after 31 January following the tax year of the disposal.

Step 2: Cost basis with share-pooling

HMRC does not let you cherry-pick which units you sold. Instead it applies share-matching rules in a strict order. For every disposal, match in this sequence:

1. Same-day rule — any acquisitions of the same token on the same day match first.
2. 30-day rule (bed and breakfasting) — acquisitions made in the 30 days after the disposal match next.
3. Section 104 pool — everything else comes out of the pooled average cost basis.

The Section 104 pool is a running weighted-average cost. Every time you buy more of the same token, the pool grows in units and in pounds. Every time you sell, you remove units at the average pool price. This is the same model HMRC applies to listed shares under TCGA 1992 and it is the single biggest difference between UK and US crypto-tax accounting. If you have ever wondered why a tool refuses to let you pick FIFO, this is why.

Read the deep dive on the 30-day bed-and-breakfasting rule if you trade actively or plan to harvest losses.

Step 3: Gain or loss per disposal

For each disposal the formula is simple once the cost basis is fixed:

Gain = Proceeds (GBP) - Cost basis (GBP) - Allowable costs

Allowable costs include:

• Exchange trading fees on both the buy and the sell.
• On-chain gas paid to broadcast the disposal transaction.
• Bridge fees that are an integral part of the swap.
• Professional valuation fees for an unusual asset.

Costs that are not allowable include cold-wallet hardware, general accountancy fees and the cost of running a mining rig (those sit on the income side instead). If you record fees correctly at the moment of the trade you usually claw back two to four percent of your taxable gain — meaningful on a busy DeFi year.

Step 4: Apply the £3,000 AEA

Sum all gains and losses across the tax year. Losses in the same year are deducted from gains automatically. Carry-forward losses from prior years are deducted only if needed to get below the AEA, and only if they were registered with HMRC within four years of the loss.

The Annual Exempt Amount for 2026-27 is £3,000. It is shared across every chargeable asset — crypto, listed shares, second homes — so a £3,000 property gain leaves nothing for crypto. Anything below the AEA is tax-free and, in most cases, does not need to be reported.

See our walk-through of claiming crypto losses with HMRC if you ended the year underwater.

Step 5: Apply the 2026 CGT rates

From 30 October 2024 the lower 10% rate was abolished for non-property gains. The 2026-27 CGT rate table for individuals is:

The rate is set by the band the gain lands in, not by the band you start the year in. Stack your gain on top of your taxable income. The portion that fits inside any unused basic-rate band is taxed at 18%; everything else is 24%.

Worked example

Sarah is a software engineer in Manchester earning £55,000 of taxable employment income in 2026-27. She made the following crypto disposals:

Net gain = £19,960 - £2,525 + £2,570 = £20,005. Subtract the £3,000 AEA: taxable gain = £17,005.

Sarah's £55,000 of income already uses her £12,570 personal allowance and the entire £37,700 basic-rate band. Every penny of her gain therefore lands in the higher-rate band and is taxed at 24%.

CGT due = £17,005 × 24% = £4,081.20. She declares the gain on SA108 and pays by 31 January 2028.

If Sarah had earned only £30,000 of income, she would have £7,700 of unused basic-rate band. The first £7,700 of taxable gain would be 18% and the remaining £9,305 would be 24% — a total bill of £1,386 + £2,233.20 = £3,619.20.

Common mistakes

• Using FIFO instead of share-pooling. US-flavoured tools default to FIFO. UK filers must switch to the Section 104 pool method or restate their reports.
• Ignoring gas fees on failed transactions. Failed on-chain transactions still cost gas, and the gas is not allowable unless it was attached to a successful disposal or acquisition. Track them but do not deduct them.
• Mixing tax years. The UK tax year ends on 5 April, not 31 December. A disposal on 6 April falls in the new year — a useful timing tool if you are close to the AEA.
• Forgetting airdrops with no service component. They are still chargeable when sold, with a zero cost basis if you did nothing to earn them. The first sale crystallises the entire market value as a gain.
• Using exchange-quoted USD prices instead of GBP. HMRC requires GBP at the moment of disposal. If the exchange only quotes USD, convert at the Bank of England spot rate for that day.
• Missing the £50,000 proceeds reporting threshold. Even with a net loss you must file SA108 if total gross proceeds exceed £50,000 in the year.

Software that does the maths for you

A spreadsheet works for under fifty disposals a year. Past that, the Section 104 pool, the 30-day rule and the GBP conversions become a full weekend of work — and a single misclassified airdrop unravels every downstream calculation. Three tools dominate the UK market in 2026.

• Koinly — built around HMRC share-pooling out of the box, generates an SA108 summary and a full transaction ledger, integrates with 800+ exchanges and wallets. Plans start at £39 for 100 transactions and scale to £179 for unlimited. The default choice for UK filers and the only tool most accountants will accept without restating.
• Coinpanda — cheaper at $49 for the entry tier, supports HMRC share-pooling and handles most DeFi protocols. Good DeFi coverage and slightly faster NFT support than Koinly. The interface is less polished but the numbers are correct.
• CoinLedger — strong on US filings, will produce a UK-style Section 104 report but you will likely need to re-map a few transactions manually. Useful if you have a mixed UK and US portfolio.

All three integrate read-only via API keys or wallet addresses, so you never expose private keys or trading permissions. Whichever tool you pick, sense-check the year-end pool balance against your own records before filing.

From calculation to SA108

A calculator is only useful if it produces something you can hand to HMRC. Whether you used a spreadsheet or a tool, the year-end output needs to map cleanly onto the SA108 Capital Gains Summary. Expect to produce four things:

• Number of disposals — every sale, swap, gift and spend counts individually.
• Total disposal proceeds in pounds, summed across every disposal.
• Total allowable costs, including the matched cost basis from the pool, the same-day rule and the 30-day rule, plus fees.
• Net gain or loss for the year, with losses separately stated so you can carry them forward.

Attach the underlying computation as a PDF to the "additional information" field. HMRC does not formally require it, but a clean working keeps an enquiry short if one ever opens. Once your numbers are filed on the SA108, pay any CGT due by the Self Assessment deadline. The official source is the Cryptoassets Manual on gov.uk.

When to pay an accountant

Crypto tax software handles the mechanical share-pooling. It does not handle judgement calls. Pay for an hour of a chartered tax adviser's time when:

• You have run a serious DeFi or yield-farming operation and need to decide where the line falls between investment and trading.
• You moved between the UK and another jurisdiction during the tax year — split-year residence rules interact with crypto in non-obvious ways.
• You received an HMRC nudge letter or are considering a voluntary disclosure for prior years.
• Your annual gain is large enough that a 1% planning improvement is worth more than the fee.

For everyone else, a tool plus a careful self-review is enough. The whole pipeline — pull data, reconcile balances, run the report, file SA108 — typically takes a focused weekend in May or June, and gets easier every year as your historical pool stabilises.