2025/26 UK Crypto Tax Year Just Ended: Your Action List

The 2025/26 UK tax year closed on 5 April 2026. Self Assessment for crypto disposals during that year is due by 31 January 2027 (or 31 October 2026 for paper returns). Nine months sounds like a lot — until you realise that HMRC's free crypto helpline is closed, exchanges take weeks to respond to data requests, and your records will be considerably more complete now than in January.

Step 1: list every wallet and exchange you used

Sit down with a piece of paper and list every place you held crypto between 6 April 2025 and 5 April 2026. That includes closed accounts. Coinbase, Kraken, Binance, BitMex, KuCoin, MEXC, exchanges that were active for one weekend during a memecoin pump, every self-custody wallet (MetaMask, Rabby, Phantom, Backpack, Trust, Ledger, Trezor), and every L2 you touched. Forgotten accounts are the single biggest cause of HMRC discrepancies.

Step 2: pull complete CSVs while data is still available

Centralised exchanges retain transaction history for varying periods. Some delete inactive accounts after 12 months. Pull CSV exports now — both "trade history" and "deposit/withdrawal history" — and store them in a folder. If you lose access to an exchange later, you will have the records.

Step 3: scan all self-custody wallets

For each public address, you need a complete list of transactions, swaps, contract interactions, staking events, and bridges between 6 April 2025 and 5 April 2026, with GBP values at execution. CryptoLens does this in one scan per address — paste the address, get the entire on-chain history priced in GBP, with Section 104 pooling already applied.

Step 4: identify the easy wins

Allowance: the 2025/26 Capital Gains Tax annual exempt amount is £3,000 per person. If you have a spouse or civil partner, transfers between you are not disposals — meaning you can use both allowances. If you realise you are over the allowance for 2025/26 but your spouse is not, gifting some assets to them before any final disposal can reduce your bill (this only applies to the 2026/27 year now — too late for 2025/26).

Losses: review for negligible-value tokens (rugged memecoins, dead L1 launches) where you can claim a loss to offset gains. Negligible value claims for 2025/26 must be made on your 2025/26 Self Assessment — you cannot back-date them once 31 January 2027 passes.

Step 5: pre-calculate now, refine in autumn

Run a draft calculation in May or June 2026. You do not need to file early, but having the number now means you can plan for the cash flow (the tax payment is also due 31 January 2027), spot any data gaps while exchanges still respond to support tickets, and avoid the December panic when HMRC's filing portal queues every UK taxpayer.

Step 6: register for Self Assessment if you have not already

If this is your first year owing crypto CGT and you do not already file, register at gov.uk by 5 October 2026. Late registration is a flat £100 penalty plus daily fines. Registration takes 10 days for the activation code to arrive, so do not leave it for January.

CryptoLens generates an HMRC-ready Capital Gains Tax summary for any UK tax year from a single wallet scan, including Section 104 pool workings for every disposal — which is exactly the document HMRC asks for if they ever query your return.