Before filing a UK tax return, gather your complete crypto transaction history, evidence of acquisition costs, sterling valuations, income records and details of transfers between your accounts. Your records should explain how you reached each figure on the return, including any losses claimed.
This guide covers individuals holding crypto personally. Start with the relevant tax year, running from 6 April to 5 April, but keep earlier transactions available: purchases made years ago can still affect today’s tax calculation.
Gather records from every account and wallet
List every exchange account, wallet and decentralised finance arrangement you used, including overseas platforms, closed accounts and wallets with no remaining balance. Note which accounts and public addresses belong to you.
Download full transaction exports covering trades, deposits, withdrawals, fees and rewards. Keep the original files alongside bank statements and transaction confirmations. A bank transfer proves money moved, but usually does not identify which tokens you bought.
Export regularly. Platforms may limit historical downloads or become unavailable, leaving you to reconstruct activity later.
Build a transaction ledger with supporting evidence
Bring your records together chronologically. For each transaction, capture:
The date, time and time zone.
The token type, blockchain and quantity received or sent.
What happened: purchase, sale, swap, reward, gift or transfer.
The transaction value in pounds sterling.
Fees, including the currency or token used to pay them.
The account or wallet involved and transaction reference or hash.
The token balance remaining after the transaction.
Retain contract addresses where similarly named tokens could be confused. Link each entry to its original export or confirmation so another person can trace it without guessing.
Public wallet addresses and transaction histories provide evidence; your accountant does not need your seed phrase or private keys.
Keep evidence of sterling values and fees
Record values at the transaction date, using an appropriate rate at the relevant time. Converting your annual dollar profit into pounds at the year-end rate will not correctly capture individual transactions.
For trades without a sterling price, retain the price source, exchange rate, timestamp and calculation. Apply a consistent, reasonable valuation method, and explain unusual estimates for tokens with little trading activity.
Keep fees separately from gross purchase costs and sale proceeds. This helps identify allowable transaction costs and prevents deducting a fee twice when an export already reports a net figure. Do not assume every platform subscription or network charge is deductible; its purpose matters.
Preserve acquisition history and pooled costs
For most interchangeable tokens UK Capital Gains Tax uses a separate Section 104 pool for each token type. This combines the relevant allowable costs across your holdings, including tokens held in different wallets or exchanges.
Keep the opening quantity and pooled cost, additions, costs allocated to disposals, and closing position. A new wallet does not reset the acquisition cost.
Same-day acquisitions are matched first, followed by qualifying purchases within 30 days after a disposal, before the remaining disposal is matched against the pool. Collect purchases after 5 April where they fall within that 30-day window.
For example, a sale on 4 April and a purchase of the same token on 12 April can affect the same disposal calculation despite falling in different tax years.
Explain transfers, disposals and crypto income
Labels in an export do not always describe the tax treatment. A withdrawal could be a transfer to your own wallet, a payment or a gift.
Match transfers between your own wallets using the sending and receiving records, allowing for fees. Moving tokens while retaining beneficial ownership is generally not a disposal. Exchanging one token for another or spending crypto normally is, even when no money reaches your bank.
For gifts, keep the recipient’s relationship to you and the market value at the transfer date. Gifts to spouses or civil partners can receive different treatment from gifts to friends.
Separately identify employment payments, mining receipts and staking rewards. Keep the amount and sterling value received, plus evidence of the arrangement. Amounts taxed as income matter when calculating a later capital gain.
For lending or liquidity arrangements, save the terms and entry and exit transactions. Whether beneficial ownership passes can affect the tax treatment; a platform’s “deposit” label is insufficient.
Reconcile the portfolio before preparing the return
Check that opening token balances, adjusted for every receipt, disposal, transfer and fee, agree with closing holdings. Investigate negative balances, duplicate imports, unmatched transfers and entries with missing acquisition costs.
Then prepare a filing pack containing your transaction ledger, capital gains calculations, income summary, closing pools and supporting files.
Keep a short list of unresolved transactions and assumptions for your accountant to review. Interface Accountants’ tax return services include preparation and review before submission with your approval.
Retain records beyond filing day
For an individual’s non-business Capital Gains Tax records, the general minimum is one year after the Self Assessment filing deadline. Self-employed business records generally need to be retained for at least five years after the relevant 31 January deadline.
Do not discard old purchase records while their costs still support tokens you own. Retain that history through the eventual disposal and applicable retention period. Store organised backups of your exports, calculations and submitted return.
FAQs
Do I need records if I only bought and held crypto?
Yes. Buying and holding normally does not create a capital gain, but purchase costs and fees may be needed when you eventually dispose of the tokens. Any rewards received need separate consideration.
Are NFTs included in the same pools as other tokens?
No. Individually identifiable NFTs are not pooled. Keep a separate acquisition and disposal history for each NFT, including its token identifier, contract address, sterling values and transaction costs.
What if an exchange has closed and records are missing?
Reconstruct activity using bank statements, emails, wallet histories and blockchain transactions. Document gaps and the basis of your calculations. Identify estimated or provisional figures appropriately when filing, and update provisional figures when actual information becomes available.