You open your exchange account to prepare your tax records, but the transaction export does not go back far enough. Another wallet contains transfers you can no longer explain. A balance on a screen is not the same thing as a usable transaction history.
There is a practical reason to organise the evidence now. HMRC warns that exchanges may retain transaction records for only a short period, or may cease operating. Keeping your own copies reduces your dependence on an account still being accessible when you need it. See HMRC's record-keeping guidance.
Start with an account map
Make a private list of the exchanges and wallets you have used, including dormant accounts. Give each one a short label. Beside it, record the period covered by your available exports and the date you last checked them. This turns an open-ended task into a visible list of gaps.
Keep this working list secure. You do not need to put wallet recovery phrases or private keys into a tax spreadsheet. Never send those secrets to a supposed tax support agent.
Download originals before editing anything
Create one folder for untouched exports and another for working files. Save each original with the platform name and export date. Preserve the file you received even if you later tidy columns, correct a duplicate or combine several accounts. Add a brief note explaining each change in the working copy.
Check that the export covers the dates you need. If it is incomplete, note exactly what is missing and request further records while access is available. Do not quietly replace a missing acquisition cost with zero or an estimate simply to make software finish its calculation.
Check the fields that matter
HMRC's guidance identifies transaction details such as token type, date, quantity, sterling value and remaining holdings, together with supporting bank records and pooled-cost information. Exchange exports can help, but HMRC says they are not tax calculations and do not track your pooled costs. Read its current guidance on disposals and records.
For your own review, add a source-file reference beside every unresolved entry. A note such as “transfer from wallet B: matching record needed” is more useful than an unexplained total. The aim of this pass is to identify evidence gaps, not to guess the tax treatment.
Do not limit the review to cash withdrawals
HMRC explains that exchanges between different cryptoassets and spending tokens on goods or services can also be disposals. Tax depends on the circumstances; a bank withdrawal alone does not define the full review. Follow the applicable UK rules, including matching and pooling requirements, rather than selecting whichever foreign cost method gives the lowest figure.
Make the next review easier
Set a recurring reminder to save new exports and resolve the oldest gaps. Keep a separate questions list for a qualified tax adviser if transactions involve complex arrangements, incomplete history or more than one jurisdiction. A tidy file helps that conversation; it does not establish the tax result by itself.
A structured place to start
The Crypto Tax Reporting & Compliance Guide includes a record-keeping section, Cost Basis Tracker, DeFi Transaction Log and an Audit Response Protocol Checklist. Use the guide's relevant country section alongside current official guidance. It is an educational reference, not a filing service or a guarantee of tax savings or compliance.
Explore the guide and instant PDF download.
General information for UK readers, checked against HMRC guidance on 19 October 2026. This is not individual tax, financial or investment advice. Rules differ between countries and editions may differ; verify current requirements and seek qualified advice where needed.