Which supporting documents must you keep for your Belgian crypto return? Practical checklist with 6 categories: exchange exports, transaction hashes, valuations and more.
Last updated: March 2026 · Reading time: 5 minutes
You have filed your crypto return. Everything checks out, the calculation is correct. And then, two years later, the tax authorities ask for proof. Do you still have it?
In Belgium, a retention period of 7 years applies to tax documents. That means you must not only be able to justify your return, but also be able to produce the underlying data. In this article we explain exactly which supporting documents you need and how best to keep them.
The short version
- Keep exchange exports (CSV or PDF) from every platform you use
- Note down transaction hashes for on-chain transactions
- Document your wallet addresses and which ones belong to you
- Keep historical prices at the time of each transaction
- Take screenshots of DeFi positions that are not exported automatically
- Generate a tax report with a transparent FIFO calculation
1. Exchange exports
Every exchange where you trade, Binance, Kraken, Coinbase, Bitvavo, offers the option to download your full transaction history as CSV or PDF. This is your primary supporting document.
Download these exports immediately after the close of each tax year. Exchanges can change their interface, limit history or even shut down. What you do not download now may no longer be available later.
Tip: Keep both the raw export and a processed report. The raw data proves what was on the exchange; the report shows how you calculated it.
2. Transaction hashes (on-chain proof)
For transactions on Ethereum, Base, Arbitrum or other blockchains, the transaction hash (tx hash) is your irrefutable proof. Every transaction on a public blockchain has a unique hash with which anyone, including the tax authorities, can verify the details: amount, timestamp, sender and recipient.
CryptoTax automatically links transaction hashes to your tax events. In your detailed report you will find the corresponding hash for each transaction.
3. Wallet addresses and links
Document which wallet addresses belong to you. This is especially important if you use multiple wallets or if there are transfers between your own addresses. The tax authorities may ask you to demonstrate that a particular address is effectively yours.
In CryptoTax, all your linked wallets are kept clearly organized. Make sure you have added all wallets and exchanges, an incomplete set leads to errors in the calculation and weaker substantiation.
4. Historical prices and valuations
The Belgian tax authorities expect you to calculate capital gains based on the actual value at the time of the transaction. That means you must be able to demonstrate the historical price for every purchase and sale.
CryptoTax automatically records the FIFO cost basis and the market value at the time of each transaction. This is included in your reports, so that your valuations are always documented and verifiable.
5. Screenshots of DeFi positions
Do you use DeFi protocols such as Aave, Compound, Uniswap or Lido? Then it is wise to periodically take screenshots of your active positions. Although on-chain data is permanent, the interface of a protocol can change or disappear.
Screenshots are especially useful for:
- Liquidity pool positions and the corresponding LP tokens
- Staking rewards and claimable rewards
- Yield farming positions with multiple tokens
Also check which crypto transactions are taxable to know which DeFi activities require additional documentation.
6. Tax report with FIFO calculation
The capstone of your substantiation is a complete tax report. This ties all the preceding supporting documents into a coherent whole: from raw transactions to calculated capital gains, with the FIFO method as the basis.
CryptoTax generates four types of exports that together form your complete file:
| Export | What it contains | What for |
|---|---|---|
| Detail PDF | All transactions with classification, valuation and tx hash | Complete audit trail |
| Summary PDF | Annual overview per tax category | Quick review and overview |
| Transactions CSV | Full transaction list in table form | Processing in accounting software |
| Disposals CSV | Sales with cost basis, proceeds and result | Detailed capital gains substantiation |
You can also share these reports with your accountant via a secure link with an expiry date. That way you work together on the same file, without emailing files back and forth. Read more about the available reports on the reports page.
Why proof is needed, even with software
A common reaction: "But I already use software, isn't that sufficient proof?" The short answer: no, not on its own.
Software calculates your taxable result, but you must be able to justify the input yourself. If the tax authorities have questions, they do not just want to see your final figure, they want to understand what that figure is based on. The combination of raw data (exchange exports, tx hashes) and a transparent report makes your return defensible.
With the arrival of DAC8, exchanges will moreover automatically report to European tax authorities. That means the tax authorities already have a reference point. Make sure your own documentation matches it.
Not sure whether a particular transaction is classified correctly? With the Tax Events Editor you can adjust classifications before you generate your report.
Practical checklist
Use this list at the end of each tax year:
- Download exchange exports from all platforms (CSV + PDF)
- Check that all wallets are linked in CryptoTax
- Take screenshots of active DeFi positions
- Generate your tax report (Detail PDF + CSVs)
- Check the classifications via the Tax Events Editor
- Keep everything in a folder per year (e.g. "Crypto 2025")
- Share the report with your accountant if applicable
Security of your data
A fair question: if you keep all that data in a platform, how secure is that?
CryptoTax works exclusively with read-only access, the software can never move or trade your crypto. All API keys are encrypted with AES-256-GCM, and your data is hosted on EU servers in Germany. Read more about the full security approach on the security page.
Conclusion
Keeping supporting documents is not a bureaucratic formality, it is your protection during an audit. With the right exports, a transparent report and a structured approach, you have nothing to worry about if the tax authorities ever come knocking.
Ready to document your crypto taxes correctly? Start for free with CryptoTax and generate your first report in minutes.
