Coinbase HMRC Letter: What to Do Next

An HMRC letter that refers to Coinbase is not a tax bill or proof that your return is wrong. It is a request that needs a careful, timely response. The safest first move is to preserve the letter exactly as received, rebuild the records for the years it names, and reconcile the figures before making any statement about tax due.

This is the Coinbase-specific evidence guide. For the response paths, deadlines, and escalation points in one place, use the HMRC cryptoasset letter action page.

Does the letter mean Coinbase reported you?

Do not assume the trigger. HMRC can obtain platform information through several channels, and the wording of your own letter is the evidence that matters. A reference to Coinbase does not show which dataset caused the contact, and it does not establish that a discrepancy exists.

Separately, current international reporting rules are expanding. Coinbase says UK customers are within its international reporting process, while UK CARF collection began on 1 January 2026 and the first reports for the 2026 calendar year are due in 2027. That future reporting timetable should not be used to guess why an earlier or current letter was sent. Read the broader CARF 2027 timeline if the letter also mentions information reporting.

Download the right Coinbase records

Start with the Coinbase transaction history and account statements for every year named in the letter. Keep the original files unchanged and work from copies. Coinbase states that its tax area covers Coinbase.com activity, not Coinbase Wallet or Coinbase Pro, so one export may be only part of the evidence.

• Coinbase.com transaction history and account statements
• Historical Coinbase Pro activity, where applicable
• Coinbase Wallet addresses and on-chain transaction history
• Deposits and withdrawals linked to bank statements
• Records from every other exchange and wallet holding the same assets
• Evidence for staking, rewards, airdrops, spending, gifts, and fees

HMRC expects individuals to keep their own cryptoasset records, including dates, transaction types, units, GBP values, cumulative holdings, wallet addresses, and supporting statements. Transfers need both sides of the evidence so they are not mistaken for acquisitions or disposals.

Five checks before you answer the letter

1. Scope: include every account, wallet, and tax year the letter asks about, not only the visible Coinbase balance.
2. Disposals: check sales, crypto-to-crypto swaps, spending, and other changes in beneficial ownership. Cash withdrawals are not the only events that can create gains or losses.
3. Income: identify rewards, staking receipts, airdrops, and payments separately from later disposals of the same assets.
4. GBP values: retain the valuation source and method used for each relevant event, including fees.
5. Matching and gaps: apply UK share-matching rules across all platforms and list unresolved transfers, missing cost basis, and unsupported classifications rather than silently guessing.

If the pooling step is unfamiliar, the Section 104 explainer shows why account-wide history matters.

Choose the response route from the reconciled facts

The letter itself controls what HMRC asked for and when it expects a response. Do not assume every letter has the same deadline or asks for the same declaration.

HMRC's disclosure service asks for the years, exchanges, transaction volumes, calculations, tax, interest, and penalties involved. After a disclosure is submitted, HMRC normally expects payment within 30 days. That is a disclosure payment rule, not a universal deadline for every crypto letter.

For a current return, the crypto Self Assessment guide explains the filing workflow. For older years, read HMRC's correction and disclosure guidance before acting.

Do not decide for yourself that the disclosure is unprompted

HMRC distinguishes prompted and unprompted disclosures by the facts, including whether a person had reason to believe HMRC had discovered or was about to discover the issue. A letter can therefore be relevant, but the label is not something to choose for a better penalty outcome. HMRC decides it. If tax may be due, get professional advice on behaviour, look-back years, penalties, and the correct route.

What ChainTax can and cannot do

ChainTax can import supported Coinbase records, combine them with supported exchange and EVM-wallet history, apply UK matching rules, and produce reviewable working with visible evidence gaps. That can help you or an adviser understand the calculation behind the response.

ChainTax does not verify whether correspondence is genuine, give tax or legal advice, decide disclosure behaviour, submit a disclosure, or reply to HMRC for you. Complex DeFi, missing history, material amounts, disputed classifications, and multi-year issues should be professionally reviewed.

Coinbase HMRC letter checklist

• Verify and preserve the full letter and enclosures.
• Calendar the exact response date printed on it.
• Download original Coinbase.com and Coinbase Pro records.
• Add Coinbase Wallet, other exchanges, wallets, and bank evidence.
• Reconcile disposals, income, transfers, fees, and GBP values.
• Apply UK matching across the complete account-wide history.
• Document missing evidence and judgement calls.
• Choose the response route only after reviewing the figures.
• Use a qualified UK tax adviser where the position is material or uncertain.

Official sources

• HMRC: tell HMRC about unpaid tax on cryptoassets
• HMRC: correct a Self Assessment tax return
• HMRC Cryptoassets Manual: keeping records
• HMRC Compliance Handbook: prompted and unprompted disclosures
• Coinbase: download transaction reports
• Coinbase: international tax reporting

This article is general information, not tax or legal advice. HMRC correspondence is fact-specific. Use the wording and deadline in your verified letter and obtain professional advice where needed.