Crypto evidence and record-keeping in 2026.

For a well-substantiated tax return, it is wise to track per platform and wallet: transaction history, deposits and withdrawals, received staking or lending rewards, and any airdrops. Also keep confirmation emails, order history and, where possible, csv exports you can download directly from the exchange or platform.

For valuation at specific moments, such as the reference date in the Netherlands, it is useful to also keep price data from the source you used, so you can later show how you arrived at a particular euro value.

Most major crypto exchanges let you download a csv export of your transaction history. This is harder for self-custody wallets, since there is no central party generating an overview; here you often have to trace transactions yourself via a block explorer or your wallet software's export function.

With multiple platforms and wallets, combining all these sources into a single overview is one of the most time-consuming steps in preparing your return. Errors or missing transactions at this stage can lead to an incorrect return, even unintentionally.

FIFO stands for 'first in, first out' and is a method for determining which specific purchase is deemed sold when you sell part of your crypto holdings. Under FIFO, the oldest purchase is assumed to be sold first, which is relevant for calculating a gain or determining the cost basis.

Not every country or situation mandates FIFO, and alternative methods exist. Consistently applying one method, and being able to explain why you chose it, matters more than the exact method itself. If in doubt, consult an adviser about which method fits your situation.

Both the Netherlands and Belgium have retention periods for records that may be relevant for taxation. For private individuals this is less strictly regulated than for businesses, but it is wise to keep relevant data for several years, certainly as long as an assessment can still be revised or corrected.

Traceability matters at least as much as completeness: an overview you can no longer explain yourself has limited value in an audit. Note briefly, therefore, why certain amounts or valuations were arrived at.

A portfolio tracker such as Block #9's (available via /portefeuille) can help bring together transactions from multiple exchanges and wallets into a single overview, including historical valuations. For Pro users, the tracker offers export options tailored to the needs of the Dutch Box 3 return and Belgian transactions, so you do not have to manually merge dozens of separate exports.

Such a tool does not replace tax advice and does not relieve you of your own responsibility to check the data, but it can significantly speed up gathering and organising data, especially when you are active across multiple platforms or use staking and DeFi.