Last reviewed: October 20, 2026.
You sell some of your crypto, send the euros to your Spanish bank account and, a few days later, the message arrives: "We need documentation proving the source of the funds." It happens often, and it pays to know what to prepare.
Why Your Bank Is Asking
It is nothing personal. Spanish banks are obliged entities under Law 10/2010 on the prevention of money laundering and terrorist financing (Ley 10/2010). This law requires them to apply due diligence measures, including understanding the nature of the client's activity and, where appropriate, the source of funds.
The Bank of Spain explains this on its Bank Customer Portal. A bank may consider certain crypto transactions high risk and require additional checks. If it takes measures that restrict your account, it must inform you and give you at least a general reason, citing Law 10/2010, unless there are special confidentiality grounds.
On top of that, the EU's DAC8 directive expands the tax information on crypto-assets that reaches the authorities. We cover it in DAC8 in Spain: What Changes in 2027.
The 4 Things You Need to Prove
Think of your explanation as a chain. Each link needs a document:
- The original money: where the euros you used to buy came from (salary, savings, sale of an asset, inheritance).
- The purchase: when, where and for how much you bought the crypto.
- The path: which exchanges and wallets the funds passed through.
- The sale and arrival at the bank: the sale and withdrawal that match the deposit the bank is reviewing.
If a link is missing, the bank will usually keep asking. The final decision always rests with the bank.
Step by Step
Step 1. Read the Request Carefully
Identify which transaction is being questioned, exactly what is requested and the deadline. If it is unclear, ask in writing what documentation they need. That way you will not have to send all your personal records.
Step 2. Gather Proof of the Original Money
- Bank statements showing the transfers to the exchange.
- If the money came from a salary, a sale or an inheritance, the document proving it (payslips, deed, acceptance of inheritance).
Step 3. Download Official Histories From Each Exchange
Use official reports (deposits, purchases, sales, withdrawals), not loose screenshots. Include accounts you have already closed, if you can.
Step 4. Document the On-Chain Movements
For funds that passed through your own wallets:
- The public addresses of your wallets and the network of each one.
- The transaction IDs (TxIDs) of the relevant movements.
A TxID proves a movement happened, but on its own it does not explain where the money came from or whether the funds are exposed to risks. For that you can use an analysis report. FundsOrigin analyzes your wallet's public address across 14 networks and generates a PDF with a Risk Score, a breakdown by network, the maximum verified amount and a verification code so the bank can check it is genuine. It does not replace the exchange statement or the bank's decision. Generate your report →
Step 5. Provide Your Tax Records
If you have already declared the gains or losses in your IRPF (Spanish personal income tax) return, attach the relevant part. If you were required to file Form 721 (modelo 721, for crypto held with providers abroad above the threshold), that helps too. We explain it in Spain's Forms 172, 175 and 721.
Step 6. Write a Short, Chronological Explanation
One page is enough: "On [date] I transferred €X from my account to exchange A (annex 1). I bought [asset] (annex 2). On [date] I moved it to my wallet [address] (annex 3). On [date] I sold it on exchange B and withdrew €Y to this account (annex 4)." Number the annexes and reply within the deadline, keeping proof that you sent it.
Step 7. Follow Up
If the bank needs more information, provide only what it asks for. If you think the measure is disproportionate, you can complain to your bank's customer service department and then to the Bank of Spain.
What You Should Never Send
- Private keys, recovery phrases or passwords. They give access to your funds and do not prove their source. No legitimate bank will ask for them.
- Edited screenshots or incomplete documents presented as complete. If information is missing, say so: making up the gaps is worse.
Common Mistakes
- Sending a CSV with no explanation that the analyst cannot interpret.
- Justifying only the final sale, without the original money.
- Contradicting what you declared to the Tax Agency.
- Waiting until there is a problem: ideally, prepare your documentation before moving a significant amount.
If It Is for a Notary (Buying a Home)
If you are buying a home in Spain with money from crypto, the notary also applies anti-money laundering rules and may ask you to justify the funds. The documentation is the same; check in advance what they will ask for.
Summary
| What to prove | Document |
|---|---|
| Original money | Bank statements, payslips, deeds |
| Purchase | Official exchange history |
| Path | Addresses, TxIDs, wallet analysis report |
| Sale and withdrawal | Exchange history and bank statement |
| Tax consistency | IRPF return and Form 721 if applicable |
Need to prove the source of your funds? Analyze your wallet and see the options available.
Official Sources
- Law 10/2010 of April 28 (BOE, in Spanish)
- Bank of Spain, "Banks can block a transfer to buy cryptocurrencies" (in Spanish)
- Spanish Tax Agency (AEAT), Form 721 FAQ (in Spanish)
This content is for information only and does not constitute tax or legal advice. A FundsOrigin report does not guarantee acceptance by your bank, notary or any other institution. Consult a professional about your situation.