Crypto Tax Checklist for Accountants: UK 2026/27

3 min read

Table of Contents

1. Scope the client’s complete crypto footprint
2. Reconcile opening and closing holdings
3. Separate income from capital events
4. Establish sterling market values
5. Build and test Section 104 pools
6. Review fees and gas
7. Identify claims and elections
8. Complete the tax return
9. Consider earlier-year disclosure
10. Prepare for CARF data matching
Practitioner review file
Official guidance

Accountants advising cryptoasset holders need more than a year-end exchange summary. A defensible 2026/27 tax file reconstructs wallets and platforms, separates income events from disposals, maintains Section 104 pools, documents valuations and reconciles the tax return to source data.

This practitioner checklist focuses on the evidence, review controls and disclosure process. For transaction classification, use our UK crypto transaction tax map.

1. Scope the client’s complete crypto footprint

Ask for every centralised exchange, wallet, hardware device, DeFi protocol, NFT marketplace and payment service used during or before the tax year. Historical data matters because current disposals can draw cost from a Section 104 pool built many years earlier.

exchange account statements and CSV exports;
public wallet addresses for each chain;
fiat bank and card deposits or withdrawals;
bridges, wrapped assets and liquidity positions;
staking, mining, lending and airdrop accounts;
NFT and token-sale activity;
lost wallets, failed exchanges and fraud claims.

2. Reconcile opening and closing holdings

For each token, reconcile opening quantity + acquisitions + income receipts − disposals − outgoing transfers = closing quantity. Unmatched withdrawals may be transfers to another client-controlled wallet, spending, gifts or undisclosed disposals. Unmatched deposits may be income, purchases, gifts or internal transfers.

Do not rely solely on transaction software. Review missing price data, unsupported chains, symbol changes, duplicate imports and transfers falsely classified as disposals.

3. Separate income from capital events

Event	Initial treatment to test	Later consequence
Purchase with fiat	No immediate tax	Creates pooled cost
Sale, swap, spending or gift	Capital disposal	Gain or loss calculation
Mining or staking reward	Trading or miscellaneous income	Receipt value becomes CGT acquisition cost
Employment reward	Employment income and possible PAYE/NIC	Later disposal subject to CGT
Airdrop	Facts determine whether income arises	Later disposal can create CGT
DeFi receipt or claim token	Ownership and contractual analysis	May be income, capital or both

4. Establish sterling market values

Every tax calculation is in pounds sterling. Record the valuation source, timestamp, exchange pair and methodology. For illiquid tokens or NFTs, contemporaneous evidence may be more persuasive than a later estimate. Use a consistent hierarchy of reliable markets and document deviations.

Where tokens are received as income, the sterling value subject to Income Tax generally becomes the acquisition cost for CGT. Reconcile the two schedules to prevent omitted or duplicated tax.

5. Build and test Section 104 pools

Maintain a separate pool for each fungible token. Apply same-day matching first, acquisitions in the following 30 days second, then the Section 104 average-cost pool. Corporate holders use different share-identification rules and should not be processed through an individual template.

Test pool quantities for negative balances, cost carried into wallets the client no longer owns, and token migrations incorrectly treated as fresh acquisitions.

6. Review fees and gas

Fees directly related to acquiring or disposing of an asset can affect allowable cost or proceeds. Network fees paid in tokens can also represent disposals of the fee token. Fees for moving assets between the client’s own wallets need separate analysis and should not automatically be capitalised or deducted.

7. Identify claims and elections

capital losses realised in the year;
unclaimed losses from earlier years;
negligible-value claims for assets that remain owned but have become nearly worthless;
spouse or civil-partner no-gain/no-loss transfers;
charitable gifts and any consideration received;
trading or miscellaneous income allowance where eligible;
foreign tax credit claims and treaty issues.

Record the statutory basis, amount, deadline and evidence for each claim.

8. Complete the tax return

Self Assessment includes a specific cryptoasset section. Reconcile:

total proceeds and allowable costs;
gains before and after losses;
income from staking, mining, lending and employment;
supporting computations and pool schedules;
other asset disposals and the £3,000 Annual Exempt Amount;
tax paid or withheld in another jurisdiction.

Use our crypto Self Assessment reporting guide for the filing route.

9. Consider earlier-year disclosure

If the reconstruction reveals unpaid tax, determine the affected years, behaviour category, assessment time limits, interest and penalties. HMRC’s Cryptoasset Disclosure Service is designed for previously undeclared crypto income and gains. The quality of the disclosure, calculations and cooperation can affect penalties. Do not simply insert all historic amounts into the current return.

10. Prepare for CARF data matching

UK cryptoasset service providers began collecting identifying information from 1 January 2026 under the Cryptoasset Reporting Framework. Reports will increase HMRC’s ability to match customers, transactions and tax returns. CARF data may not contain the full acquisition-cost history or self-custody activity, so advisers still need an independent reconciliation.