UK Crypto Tax 2026/27: Complete Filing Walkthrough

The 2026/27 UK tax year runs from 6 April 2026 to 5 April 2027, with a Self Assessment deadline of 31 January 2028 for online returns. If you sold, swapped, staked, gifted, or spent any crypto during that window, HMRC almost certainly wants to hear about it. This guide walks you through the whole process end-to-end so you know exactly what to do — no surprises in January.

What's changed for 2026/27

The Capital Gains Tax annual exempt amount is £3,000 — the same as 2025/26, but a fraction of the £12,300 it was in 2022. Rates for crypto gains are 18% for basic-rate taxpayers and 24% for higher/additional-rate. Income Tax rates apply to staking rewards, airdrops classified as income, and mining proceeds — 20% / 40% / 45% depending on your total income band.

The big compliance change is the OECD Crypto-Asset Reporting Framework (CARF), which took effect on 1 January 2026. UK-based exchanges and any exchange serving UK customers now automatically report your transactions to HMRC each year. That includes Binance, Coinbase, Kraken, and Crypto.com. HMRC already has your data — they just want to see whether your Self Assessment matches it. This is why the wave of "nudge letters" started in 2025 and will continue into 2027.

Step 1: Gather every transaction

You need a complete list of every disposal in the 2026/27 tax year. A disposal is any of the following:

- Selling crypto for GBP or another fiat currency - Swapping one token for another (yes, USDC → USDT counts) - Spending crypto on goods or services - Gifting crypto to anyone other than your spouse or civil partner - Contributing crypto to a liquidity pool (in most interpretations)

Wallet-to-wallet transfers between wallets you control are not disposals. Staking a token in the same protocol is generally not a disposal, but the reward earned is income at receipt value.

Pull exports from every exchange you used, plus on-chain transactions from every wallet address you own. CryptoLens does this in one step: paste each address, connect each exchange or import its CSV, and the platform builds the full ledger.

Step 2: Apply HMRC's matching rules

HMRC does not let you cherry-pick which coins you sold. You must apply three rules in order, for each disposal:

1. **Same-day rule** — match the disposal against any acquisitions of the same asset on the same day. 2. **30-day rule (bed & breakfast)** — match remaining disposal against acquisitions in the next 30 calendar days. This prevents "wash" trades where people sell then re-buy to crystallise a loss. 3. **Section 104 pool** — anything left is matched against the pooled average cost of all your prior holdings of that asset.

Most people get this wrong when doing it by hand. It matters because your realised gain — the number you pay tax on — can be dramatically different depending on how it's matched.

Step 3: Add up gains, deduct losses

Sum your gains from all disposals. Subtract allowable losses from the same year. Losses can also be carried forward from prior years (as long as you registered them within four years of the year they were made). Then subtract the £3,000 annual exempt amount. Whatever is left is your taxable gain.

Step 4: Fill out SA108

The SA108 "Capital Gains Summary" is the form that accompanies your main SA100 Self Assessment. For crypto you'll typically use the "Other property, assets and gains" section. You need:

- Number of disposals in the year - Total disposal proceeds - Total allowable costs (including your Section 104 pool cost basis) - Total gains - Total losses - Any losses brought forward that you're using this year

You do not need to send HMRC a transaction-by-transaction schedule with the return, but you must keep one for at least six years after the filing deadline in case they open an enquiry. A one-click PDF from CryptoLens covers this.

Step 5: File and pay

Register for Self Assessment by 5 October 2027 if you haven't already. File your return online by 31 January 2028. Pay any tax due by the same date. HMRC's late-filing penalty is £100 the day after the deadline, escalating fast — do not miss it.

Common mistakes that trigger enquiries

Failing to report token-to-token swaps is the number one issue. Failing to include DeFi activity (Uniswap trades, Aave lending, LP entries and exits) is number two. Reporting only your GBP off-ramps and pretending the other 200 trades didn't happen is number three — and CARF data now makes this trivially detectable.

The cleanest path from here

Whether you have 15 transactions or 15,000, the workflow is the same: consolidate your ledger, apply HMRC's rules correctly, generate a summary you can defend, and file. CryptoLens does the first three in one shot — paste your wallets, drop your exchange CSVs (including Revolut), and get a filing-ready SA108 summary for £4.99/month with a 30-day money-back guarantee.