The task in brief
You keep a complete, dated record of every crypto asset you buy, sell, swap or receive, so that you can work out gains and losses when tax is due. Crypto assets are digital tokens, and much of the activity around them happens inside exchanges and wallets run by other businesses. Because that activity is split across several businesses, your own records may be the only complete picture you have.
Before you start
- Find out which tax authority covers you and read its guidance on crypto assets, since rules differ between countries and change over time.
- List every service you have used, including exchanges, wallets, and any card or payment service that touched crypto assets.
- Confirm that you can still reach each account and that its download options work before you begin.
Which records to keep
For every transaction, keep the date and time, the type of action, the asset name, the quantity, and the amount in the currency your tax authority uses. Record what you gave up as well as what you received, because a sale or a swap is often the event a tax system measures. Transfers between your own wallets need the same detail, since they are often treated differently from sales. Keep the reference number each service gives a transaction, so you can match both sides of a transfer later.
Cost basis methods in concept
Cost basis is the amount you paid for an asset, including the expenses of buying it, and it is subtracted from what you received when you sell to work out a gain or loss. Most investors buy the same asset in several batches at different prices. A cost basis method is the rule that decides which batch counts as sold when you sell part of a holding.
Common approaches include first in first out, last in first out, average cost, and specific identification, where you name the batch yourself. Your tax authority may accept only some of these, and it may require you to apply a single method consistently. Keep enough detail that you could recalculate your history under any permitted method, not only the method you used last time.
Steps to keep the records
Exports matter because each service records only its own side of your activity, and it may not keep the full history available forever. A tax tool then reads the combined history, applies the cost basis method you choose, and produces gains and losses for the period. It can only work from the data you give it, so the checks below still matter.
- Export the full transaction history from each service in the most detailed format it offers, usually a spreadsheet or comma-separated file.
- Save every export in a dated folder, and never overwrite an earlier export, because a service may later change what its history contains.
- Check each export against your own memory and any bank or card statements for the same period, and note any gaps.
- Merge the exports into a single master sheet with consistent columns, and match transfers between your own wallets so they are not counted as sales.
- Add the amount in your tax authority's currency for each row, and write down the source you used for each conversion.
- Import the combined history into a tax tool and select a cost basis method that your tax authority permits.
- Compare the tool's totals with your master sheet, check a handful of rows by hand, and keep both the raw exports and the final report.
When an export has gaps or wrong totals
If an export is missing rows or your totals do not match your records, do not guess the missing figures. Go back to the service, look for the period that is missing, and ask for a full statement through its official route. Keep a written note of each gap and what you did about it, so you can explain the figure later.
When the tool's result looks wrong, calculate a single transaction by hand. Matching results suggest the tool is reading the rows correctly. Different results mean you should trace which input caused the gap before you rely on either number. If a gap stays unresolved, a qualified accountant in your country can explain your options.
Record exports as a reason to pick a service
Record keeping is an area where providers differ in practice. Some make full history exports easy to find, while others make them hard to get or limit the detail they include. Look for clear export options, consistent file formats, and a history that stays accessible for as long as you need it. The guide to choosing investment platforms covers other points to compare alongside these.
Also review how a provider protects and records the assets it holds, using the safety guide for providers. Account structure affects reporting too, so read about account types before you commit money.
Tax rules vary by country and change over time, so check your tax authority's guidance and the provider's own information. Doing that early makes the records far easier to keep.