What to have ready before you start
- Author
- CRYPTO PORT Editorial
- Published
- Updated
- Reading time
- 6 min
In short
Most of what stalls a crypto return is missing material, not difficult arithmetic. Pulling together exchange history, wallet records, cash movements and last year's closing figures before you start will cut the number of times you grind to a halt. Check the National Tax Agency's guidance for what is actually required, and ask a tax accountant about anything unclear.
Key points
- List every account and wallet you have ever used, including dormant ones
- Without last year's closing quantities and cost basis, this year cannot be calculated
- Bank records of yen in and out are useful for cross-checking
- Assemble it all first — hunting for pieces mid-calculation is how gaps appear
Definition
The preparation step of collecting the records and carry-forward figures you need in one place before starting to calculate and fill in a return.
Start with an inventory of accounts and wallets. Not just the ones you use now — everything you touched during the year, anything holding a forgotten remainder, anything whose operator has announced a closure. An account missed here will be missed in the calculation too. Searching your inbox for exchange names often surfaces one you had forgotten.
Next, check what carries over from last year. Crypto cost basis runs across year boundaries: without knowing what you held at the end of the previous year and what it cost, this year's disposals cannot be worked out. If you used a calculation tool last year, retrieve its closing balance report. If this is your first calculation, you will need to go back to when you started trading.
There are broadly four kinds of records to gather: exchange trade and deposit/withdrawal history; transfers in and out of self-custody wallets; receipts of rewards from staking, lending and similar; and bank statements. The bank statements are not crypto records, but matching yen movements against them is a good way to notice that a deposit to an exchange never made it into your data.
It also helps enormously to write a plain-language note of what happened during the year — 'moved funds from exchange A to exchange B in spring', 'sold an NFT in summer', 'migrated wallets in autumn'. Months later, when you are chasing an unexplained difference, having that note is the difference between ten minutes and an afternoon.
Finally, what you are actually required to prepare and retain is set by rules that get amended. The list above is a practical one, not a legal one. Confirm the formal requirements in the National Tax Agency's guidance and take anything uncertain to a tax accountant.
Watch out for
- · This page is a general orientation, not tax advice
- · Never write a seed phrase or private key into any of these record files
- · The scope of documents you must retain is set by the rules — check National Tax Agency guidance
Frequently asked questions
Do I need to include an account with only a tiny balance left?
Deciding on the basis of size alone is not advisable: even small activity feeds the calculation, and an omitted account is a common reason balances refuse to reconcile. List everything first, then take any judgement calls to a tax accountant.