You sell part of your crypto, deposit €30.000 into your bank account, and a week later you get an email from your bank: "Please demonstrate the origin of these funds within 14 days". Or worse: your account is already frozen pending an AML investigation. It happens more often than you think, and without a well-documented file you can be locked out of your money for weeks.
You sell part of your crypto, deposit €30.000 into your bank account, and a week later you get an email from your bank: "Please demonstrate the origin of these funds within 14 days". Or worse: your account is already frozen pending an AML investigation. It happens more often than you think, and without a well-documented file you can be locked out of your money for weeks.
Belgian banks are required under anti-money-laundering law (AMLD directives, implemented in the Act of 18 September 2017) to verify the origin of funds for suspicious or unusual transactions. Crypto income is often automatically flagged as high risk by bank risk engines. In this guide: how to build a proof of funds file, which documents you need, and what you can do if your account is already frozen.
The short version
- Proof of funds proves the origin of a specific deposit (this €30.000 comes from this sale on this exchange)
- Source of wealth proves your overall financial story (why you hold crypto of that size in the first place)
- Banks accept exchange statements, transaction hashes and cost basis reports as evidence
- A Cryptotax detail report consolidates all on-chain and exchange data into one document, ready for the compliance department
- If your account is frozen: respond within the set deadline, do not submit an incomplete file, and involve a lawyer if the freeze lasts unreasonably long
- Proof to your bank is not the same as proof to the tax authority, but the underlying documents largely overlap
Why banks suddenly ask questions about crypto
Since 2023, Belgian banks (KBC, BNP Paribas Fortis, ING, Belfius and neobanks such as Revolut and Wise) have been ramping up their AML monitoring significantly. The drivers:
- MiCA and the sixth European anti-money-laundering directive (AMLD6) require detailed origin checks for crypto-related flows.
- The Financial Intelligence Processing Unit (CFI/CTIF) receives more than 40,000 suspicious transaction reports annually, and crypto deposits score disproportionately high in those statistics.
- Banks carry their own liability: if money laundering passes through your account, they risk fines running into the millions. Better too strict than too lenient.
What triggers a review? Typically one or more of these signals: a deposit above €10.000, a deposit from an exchange (Kraken, Binance, Coinbase, Bitvavo) you have never used before, an irregular pattern compared to your normal account activity, or a deposit in a SEPA transfer with "crypto" in the reference field.
Proof of funds versus source of wealth
Banks use two distinct concepts that are often confused:
| Concept | What do you prove? | Example document |
|---|---|---|
| Proof of funds | The origin of one specific transaction or balance | Exchange execution confirmation of the sale that generated €30.000 |
| Source of wealth | Your overall financial history and why you hold funds of that size | Purchase history from 2017 to today, including interim trades and holdings |
For a one-off payout, your bank usually only asks for proof of funds. For larger amounts (from around €50.000) or in private banking relationships, source of wealth is added on top. Prepare for both.
Documentation checklist
This is the core of a strong file. The more of these you can provide, the faster the bank will be satisfied.
- Exchange statement of the sale. Almost all exchanges (Binance, Kraken, Coinbase, Bitvavo) provide a PDF statement or CSV with date, asset, sale price in EUR and the destination account number. Download this directly after every EUR withdrawal.
- Transaction hash of the on-chain transfer. If you first sent crypto from your own wallet to the exchange, include the tx hash. The bank can verify via a block explorer that the address belonged to you.
- Purchase proofs or historical trades. Purchase invoices from the original acquisition (often years ago), or a complete overview of trades that led to the current position. This is where the cost basis calculation comes in.
- Proof of wallet ownership. A signed message from the wallet address, or a small incoming transfer from the address to the exchange, confirms that the wallet is yours. Tools such as Etherscan support "Sign Message".
- Identification of earlier fiat deposits. Show that the EUR you originally put into crypto came from your salary, a bonus, an inheritance or a property sale. This is where source of wealth makes the difference.
- Tax return with crypto reporting. If you have already declared crypto capital gains or staking income in previous years (see also DAC8 in Belgium), that is a strong argument: your activity has been properly declared for tax purposes.
- Cryptotax detail report. One PDF that consolidates all of the above in chronological order, including tx hashes and EUR valuations at the time of each transaction.
Cryptotax reports as evidence
The problem with separate exchange CSVs and block explorer screenshots: a compliance officer at the bank has to spend hours piecing together a coherent story. A consolidated report does that work upfront.
Cryptotax generates four exports that together form a proof-of-funds file:
| Export | What it contains | Useful for |
|---|---|---|
| Detail PDF | Complete transaction history per wallet and exchange, with tx hashes, EUR valuations and classification | The main document you send to the bank |
| Summary PDF | Annual overview per category (capital gain, staking, airdrop) | Quick context for the compliance officer |
| Disposals CSV | List of all sales with cost basis and proceeds | Specific substantiation of the sale that funded the deposit |
| Transactions CSV | Raw transaction list | For review or referral to your accountant |
The reports are generated on the basis of read-only data: your API keys and wallet addresses give Cryptotax insight into your history, but never the right to move funds. Read more about how it works on the security page.
Tip: use the shareable report link to share your file directly with the compliance department, with an expiry date. That way you do not need to send sensitive PDFs by email.
What to do if your account is frozen
A freeze is intended as a temporary measure while the bank fulfils its AML obligations. In practice, however, it can last weeks to months. A structured escalation route:
- Read the letter or email carefully. Banks always give a deadline (usually 14 or 30 days) and a contact person (often the "compliance department" or "AML team"). Do not miss that deadline.
- Call your relationship manager. At retail banks this is often your branch manager, at private banking your dedicated banker. They can speed up internal escalation.
- Submit a complete file all at once. Do not send documents piecemeal. One PDF with your Cryptotax detail report plus exchange statements plus a short cover letter ("below is the timeline of my crypto activity and the origin of the deposit of [date]") works much better.
- Keep all correspondence. If the matter escalates, you will need a timeline and emails. Where possible, send a registered letter with your first response.
- Complaint to the mediation service. If the bank does not respond or the freeze lasts unreasonably long, file a complaint with the Ombudsman for Financial Disputes (Ombudsfin). This is free and the bank is obliged to cooperate.
- Legal action. For large amounts or prolonged freezes, summary proceedings (référé) before the court of first instance are an option. A lawyer specialising in financial law can force a ruling within a few weeks.
Important: avoid one common mistake. Some people deposit "explanatory" extra amounts or open a second account to work around the freeze. The bank reads this as suspicious behaviour and reinforces the AML suspicion. Always work through the official channel.
Proof to the bank versus proof to the tax authority
A common misunderstanding: that your bank file is automatically ready for the tax authority too. The documents overlap, but the focus does not.
| Aspect | Bank (AML / KYC) | Tax authority (tax return) |
|---|---|---|
| Purpose | Proof of lawful origin, no money laundering | Proof of correctly calculated capital gain and taxable income |
| Key document | Exchange statement and proof of wallet ownership | Tax report with cost basis calculation per asset |
| Legal basis | Act of 18 September 2017 (anti-money-laundering) | Art. 90, 9° WIB 92 (capital gains tax from 2026) |
| Retention period | 10 years (AML file held by bank) | 7 years (tax documents) |
| What if evidence is missing? | Account frozen, transaction refused | Assessment by default, tax surcharge |
Practical: build one file with all underlying documents, and repackage the summary explanation for each authority. The Cryptotax detail report works for both, but add a cover letter about the specific deposit for your bank, and the capital gain calculation per asset for the tax authority.
More on the tax side: which supporting documents to keep for your crypto tax return and the step-by-step guide for the 2027 tax return.
FAQ: frequently asked questions
My bank is asking for proof of funds, but I have only held my crypto for a year. Is that a problem?
No, as long as you can demonstrate the purchase history. Show the original EUR deposit to the exchange, the purchase transaction, and the eventual sale. The fewer gaps in the chain, the stronger your file.
Can I produce proof of funds for a DeFi position (Uniswap, Aave)?
Yes. Cryptotax includes DeFi transactions in the detail report, including LP tokens, lending positions and yield. For the bank: add a brief explanation of what the protocol does and provide the relevant tx hashes. See also DeFi loans in Belgium.
Can the bank simply refuse to accept a deposit?
Under the anti-money-laundering law, yes, provided they notify the Financial Intelligence Processing Unit (CFI/CTIF). You have the right to a reasoned explanation and to the Ombudsfin procedure if the refusal is not resolved.
What if I bought my crypto from a friend or family member (OTC)?
That is harder to prove. Ask the counterparty for a private agreement (date, amount, wallet addresses) plus a copy of their identity document. Without paperwork, this is a weak part of your file.
I have held my crypto for years and my old exchange no longer exists (think Mt. Gox, Cryptopia). What now?
Collect what you have: old email confirmations, archive.org screenshots of your dashboard, bank statements from the original EUR deposit. Cryptotax can import these manual purchases via CSV so that they are included in the report. The file will be weaker, but often acceptable together with a written explanation.
How long can a bank freeze my account?
Not indefinitely under the law. After a CFI notification, FOD Financiën (the Belgian tax authority) has in principle five working days to intervene, and without a decision to seize the freeze lapses. In practice, banks often extend that period through their own AML procedures. A well-substantiated file cuts this time drastically.
Try it today
Generate a complete file of your crypto activity before your bank asks for it. Start for free with Cryptotax, connect your wallets and exchanges read-only, and export a detail report in minutes that you can send directly to your compliance department.
Accountants and tax advisers: the accountant portal lets you build proof-of-funds files for multiple clients in parallel, with audit-ready exports.
Disclaimer: This article is purely informational and does not constitute individual legal or tax advice. For a concrete account freeze or a complex AML file: consult a lawyer specialising in financial law or a qualified Belgian tax adviser.
