saver
Individual with crypto savings
“You bought years ago and now want to sell and deposit the money in your bank. The bank will ask you to prove where the initial capital came from and the whole path up to the deposit.”
Crypto Source of Funds in Spain
We prepare a solid dossier to prove where your crypto came from: source of funds (SoF), on-chain traceability with TxIDs, exchange statements and a clear narrative to respond to your bank, the Spanish Tax Agency (AEAT / Hacienda), a notary or auditors. When you are asked for explanations, what matters is not what you say but what you can prove.
Free consultation
We reply within 24 h
- Form 721 (Modelo 721) threshold
- €50,000
- Balance reference date
- December 31
- Travel Rule applies from
- Dec. 2024
- EU tax data exchange on crypto
- DAC8
Concept
What does proving the origin of your crypto mean?
Proving the origin of your crypto means being able to explain and back up with evidence where the money comes from and the path it has taken: how it was acquired, where it moved (wallets and exchanges) and what was done with it. The key is not “what you say”, but that your story is consistent and the evidence verifiable.
It almost always comes down to a simple chain that any reviewer understands: fiat source → purchase → movements → sale → deposit. When that chain is documented from start to finish, the bank, the Tax Agency or an auditor can follow it without friction. When a link is missing, the blocks and information requests begin.
When you need it
Who asks you to prove the origin of your crypto?
What you need to prove depends on who is asking, but the documentary basis is the same. These are the situations in which you will be asked for explanations and evidence.
Bank
Proving the origin of crypto to a Spanish bank
When you receive funds from exchanges or when there are unusual movements, the bank asks you to prove the full chain (fiat source → purchase → movements → sale → deposit) to meet its anti-money laundering obligations.
Learn more →
SoFbanking
Exchange
Source of Funds / Source of Wealth
Source of funds reviews, operating limits, internal audits or compliance requests from the exchange or provider when the amount or the pattern triggers them.
Learn more →
SoWKYC
Tax Agency
Tax information requests
Proving gains and losses, the origin of the money and wealth consistency. Without clear support for purchases, sales and income, errors multiply in a tax audit.
Learn more →
taxconsistency
Notary
Property and asset transactions
Buying real estate or other assets with funds that include crypto: you need to document the provenance and legitimacy of the money before signing in front of a notary.
Learn more →
provenancedue diligence
Audit
Due diligence and investors
Partners, investors or auditors who require evidence of the origin of the funds and risk control over your crypto activity, with a report that can be presented to third parties.
Learn more →
investorsreport
DeFi · Wallets
Self-custody and DeFi
If there is DeFi, bridges or swaps involved, you need a traceability report: addresses, TxIDs, dates and an explanation of why each movement was made.
Learn more →
on-chainTxIDs
The dossier
Anatomy of a complete dossier
A good dossier is a folder with an index and evidence, organized so that any reviewer can follow it in minutes. These are the blocks it cannot do without.
Traceability
Reconstructing the on-chain path
With self-custody, DeFi, bridges or swaps, what usually fails is not legitimacy but understanding. A traceability report reconstructs the path with addresses, hashes and dates, and reduces suspicion.
Profiles
Who needs it?
If at some point you are going to move your crypto into the fiat world, buy something significant or get paid in crypto, someone will ask you for explanations. Better to have the dossier ready before they ask.
trader
Active trader or investor
“With many trades, several exchanges and wallets, rebuilding the history after the fact is slow. Exporting the CSVs in time and organizing the traceability saves you nasty surprises with the bank and the Tax Agency.”
business
Company or self-employed person paid in crypto
“Invoices paid in crypto, conversions to euros, and accounting and tax consistency. You need documentary support linking each payment to its invoice and to the deposit in your account.”
self-custody
DeFi and self-custody user
“If you use your own wallets, DeFi, bridges or swaps, the key is on-chain traceability: addresses, TxIDs and a clear explanation of why the funds were moved.”
Why it matters
What happens if you can’t prove it
When you are asked for explanations, what matters is not what you say but what you can prove. These are the problems that arise when documentary support is missing.
Bank blocks and delays: deposits held or operating limits imposed while the bank reviews the source of funds and the traceability.
Information requests and paperwork stress: if history is missing (CSV, TxIDs, supporting documents), rebuilding your activity after the fact is slow and sometimes impossible.
Tax risk and inconsistencies: without clear support for purchases, sales and income, it is easy to make mistakes or be unable to prove your story to the Tax Agency.
Commingling of funds: mixing your own money with third parties’ money without records triggers suspicion and makes it hard to separate what is yours and where it comes from.
Untraceable movements: transfers between wallets without TxIDs or a timeline turn legitimate activity into something impossible to explain.
Fragmented activity: many exchanges and wallets without an executive summary tying the story together mean that nobody understands the whole picture.
Have you been asked to prove the origin of your crypto?
If there is already a block or an information request, or you want to get ahead before selling, we prepare the dossier: source of funds, traceability, statements and narrative, so you can respond with a defensible package.
Depending on who asks
Who is asking, and what do they want to see?
Proving the origin of your crypto changes depending on who asks. The documentary basis is the same, but each party looks at different things.
What makes a good dossier
Compared with “a pile of loose screenshots”, what makes the difference is a file that is consistent, verifiable and easy to follow.
- Consistency
- The story adds up from start to finish, with no gaps.
- Verifiable
- Every statement has its evidence attached.
- Order
- Index, dates and annexes so it can be read in minutes.
- Narrative
- An executive summary that ties it all together.
How we prepare it
We build the dossier with an index and evidence, ready to send. A standard file is usually ready in 5–10 business days; if there is already a block or an information request, we prioritize it.
- We gather the source of funds, exchange history and on-chain traceability.
- We link purchases, movements, sales and deposits to their evidence.
- We draft the executive summary and assemble the folder with annexes.
| Who asks | What they focus on | Recommended evidence |
|---|---|---|
| Bank | Source of funds and consistency with anti-money laundering rules | Statements, KYC, exchange CSV, sale and proof of deposit |
| Exchange | Source of Funds / Source of Wealth | Fiat source, proof of purchase and traceability in date order |
| Tax Agency | Tax result and wealth consistency | Activity, costs, income and support, with no unexplained “gaps” |
| Notary / due diligence | Provenance and legitimacy of the funds | Complete dossier plus an on-chain traceability report |
Cross-cutting tip: a 1–2 page executive summary at the start of the dossier speeds up any review. Indicative table; this page is for information only and does not constitute legal or tax advice.
Frequently asked questions
Crypto source of funds: frequently asked questions
What does proving the origin of your crypto mean?
Being able to explain and back up with evidence where the money comes from, how it was acquired, where it moved and what was done with it. The key is a consistent story and verifiable evidence, not fine words.
Who can ask me to prove the origin of my crypto?
Banks, exchanges, the Tax Agency, notaries, auditors, partners and investors. If your activity includes self-custody, DeFi or several wallets, it is worth preparing the dossier before you are asked.
What documentation do I need?
Fiat source, proof of purchase, exchange history (CSV), on-chain traceability (TxIDs), proof of sale or conversion, staking or airdrop income if applicable, an executive summary and tax support where appropriate.
What happens if I can’t prove it?
Bank blocks, information requests, operational delays and tax risk. Rebuilding your activity after the fact is slow, expensive and, if the history has been lost, sometimes impossible. Getting ahead of it is much cheaper than responding in a rush.
Do I need a traceability report?
If there is self-custody, DeFi, swaps or bridges, yes: the traceability report reconstructs the on-chain path with TxIDs, addresses and a verifiable narrative. For activity only on exchanges with KYC, a standard dossier is usually enough.
How much does it cost to prepare a dossier?
It depends on complexity: the number of exchanges, wallets and transactions, and whether DeFi or bridges are involved. We give you a tailored quote after a free initial consultation.
How long does it take?
A standard dossier is usually ready in 5–10 business days. If there is already a block or an information request with a deadline, we prioritize it so you can respond as soon as possible.
Does it work for both the Tax Agency and the bank?
Yes. The dossier is adapted to the recipient: for the bank, the focus is the source of funds and anti-money laundering; for the Tax Agency, tax and wealth consistency. Both share the same documentary basis.
What if I lost the history of an exchange that no longer exists?
Not all is lost. It can usually be reconstructed from the bank statements showing SEPA transfers to and from that exchange, confirmation emails, and the on-chain traceability of withdrawals to your wallets. The sooner you tackle it, the more can be recovered.
Can I prove the origin of crypto bought many years ago?
Yes, although it takes more reconstruction work. The age of the holdings works in favor of legitimacy if the initial fiat source and the subsequent chain are well documented. What matters is to start gathering evidence before it is lost.
People also ask
SoF, TxIDs, tax reporting and the Travel Rule
What are Source of Funds (SoF) and Source of Wealth (SoW)?
Source of Funds is the specific origin of the money in a transaction (where that capital came from). Source of Wealth is the origin of your wealth in general (how you came to have it). Banks and exchanges usually ask for one or the other, or both.
What is a TxID and why does it matter?
A TxID (transaction identifier or hash) is the unique “fingerprint” of each transaction on the blockchain. It allows a movement to be located and verified objectively, which makes it the core evidence of on-chain traceability.
Do I have to declare my crypto?
It depends on your case. Gains are taxed under Spanish personal income tax (IRPF); Form 721 (Modelo 721) applies to crypto held in custody abroad when the combined balance exceeds €50,000 at December 31; and Spanish platforms have their own reporting obligations. Declaring and proving are different but complementary: see Tax Agency audits of crypto.
Does self-custody (your own wallet) also need to be proven?
For source of funds purposes, yes: even if the wallet is yours, you have to explain how the funds got there and the path they took. For Form 721 purposes, however, crypto in self-custody (with your own keys) does not count, because it is not held in custody by a third party abroad.
What is the difference between proving and declaring crypto?
Declaring means meeting your tax obligations (IRPF, Form 721, etc.). Proving means showing, with evidence, the origin and path of the funds to whoever asks. You can have everything declared and still need to prove the origin to your bank.
How does the Travel Rule affect my transfers?
Since December 2024, the Travel Rule requires exchanges to make crypto transfers travel with originator and beneficiary data. This creates more traceability “by default”, but it does not replace your source of funds dossier: they are complementary layers.
What is DAC8 and how does it affect me?
DAC8 is the EU directive that extends the automatic exchange of tax information to crypto-assets, so that tax authorities receive data from providers. In practice it strengthens transparency and makes it even more advisable to keep your activity documented and consistent.
Practical guide
Documentation to prove the origin of your crypto
Everything worth gathering for a complete, defensible dossier. Order matters: first the origin, then the path, then the result and, finally, the narrative that ties it together.
What counts is what you can prove
“I made it with crypto” is not enough. Every link in the chain needs its evidence: statements, receipts, CSVs, TxIDs and proof of deposit.
Sort by date and connect
Activity fragmented across several exchanges and wallets becomes readable when it is put in chronological order and each movement is linked to its proof.
The executive summary comes first
A 1–2 page document that tells the story (origin, activity, routes and conclusion) is the first thing a reviewer reads, and it sets the tone.
Checklist: the dossier in 10 steps
- Gather the fiat source of funds: statements, payslips, invoicing, asset sales or inheritances.
- Gather proof of purchase and entry into crypto: SEPA transfers to the exchange, receipts and dates.
- Export the full exchange history (trades, deposits, withdrawals, fees and KYC) as CSV.
- Document the on-chain traceability: addresses, TxIDs and a timeline of the movements.
- Gather proof of sale or conversion to euros: price, date, fees and proof of deposit.
- Record staking, airdrop or mining income, with payouts and valuation criteria.
- Write the narrative: a 1–2 page executive summary with the full story.
- Prepare tax support if applicable: calculation of gains and losses, costs and dates.
- Check wealth consistency: that your activity matches your declared wealth.
- Assemble the final folder with an index and annexes, in a PDF ready to send.
Self-custody or DeFi involved? Add a traceability report. Tax questions? See Tax Agency audits of crypto and banking crypto proceeds.
How we prepare it
From source of funds to the final folder
We build the dossier as an ordered sequence (origin, exchange, traceability, sales and tax and final folder) so that it can be sent and defended.
1) OriginSource of funds (SoF/SoW)
We prove where the initial capital came from with statements, payslips, invoicing or asset sales, and connect the bank with the exchange.
- fiat
- statements
- SEPA
2) ExchangeExchange history
We gather and organize trades, deposits, withdrawals, fees and the account holder’s KYC, with CSV exports and official reports.
- CSV
- trades
- KYC
3) TraceabilityOn-chain traceability
Where needed, we reconstruct the path with addresses, TxIDs and a timeline, and explain the reason for each movement to reduce suspicion.
- wallets
- TxIDs
- KYT
4) Sales + taxSales, conversion and tax support
We document sales and conversions to euros, bank deposits and, if applicable, the calculation of gains and losses with its backup.
Goal: a dossier that is consistent, verifiable and quick to review, with no unexplained gaps.
Quick decisionMap: what do I need?
exchanges only (KYC)
A standard dossier is usually enough: origin, history and sales.
DeFi / self-custody
Add an on-chain traceability report with TxIDs and narrative.
block or information request
We prepare a prioritized, defensible response package.
Playbook
What your dossier must be able to prove
Ownership
That the accounts and wallets are yours.
KYC, screenshots and message signing.
Origin
Where the initial capital came from.
Statements, payslips, asset sales.
Path
Where the funds moved.
Exchange CSV, TxIDs and timeline.
Result
What was done and how it adds up.
Sales, deposits and tax calculation.
Consistency
That everything fits with your wealth.
An executive summary that ties it together.
Mistakes that stop you from proving the origin of your crypto
Anticipate them: almost all can be avoided by gathering evidence in time and building an organized folder.
- Being unable to explain the fiat source (just “I made it with crypto”).
- Losing the exchange history or not exporting the CSV in time.
- Mixing your own funds with third parties’ funds without records.
- Moving funds across wallets without TxIDs or a timeline.
- Fragmented activity, with no executive summary to tie it together.
Glossary
Key concepts for proving the origin of crypto
These terms come up when a bank, an exchange or the Tax Agency asks you for explanations about your crypto.
SoFbasics
Source of funds
Source of Funds: the specific origin of the money in a transaction. Where that particular capital came from.
What banks ask for most.
SoWwealth
Source of Wealth
The origin of your wealth in general: how you came to have it, beyond any specific transaction.
Common for large amounts.
on-chainproof
On-chain traceability
Reconstruction of the path of the funds on the blockchain using addresses, hashes and dates.
The heart of the report.
TxIDdata
TxID
Unique identifier (hash) of a transaction on the blockchain. It allows a movement to be located and verified objectively.
The “fingerprint” of each transaction.
KYCidentity
KYC
Know Your Customer: the identity verification carried out by the exchange. It shows who the account holder is.
Documents ownership.
KYTrisk
KYT
Know Your Transaction: risk analysis of transactions and addresses (clustering, exposure to illicit funds).
Strengthens traceability.
self-hostedwallet
Self-custody
A wallet whose private keys you control, with no third-party custodian. You need to explain how the funds came in and went out.
Does not count for Form 721.
DeFiactivity
DeFi
Decentralized finance: swaps, pools, bridges and protocols with no intermediary. It complicates traceability if it is not documented.
This is where the report is key.
CEXplatform
Exchange
Centralized exchange platform (with KYC and custody). Its history (CSV) is one of the most important pieces of evidence.
Export the CSV in time.
consistencytax
Wealth consistency
Your activity and income fit with your wealth and with what you have declared. No unexplained gaps or jumps.
What the Tax Agency reviews.
M-721obligation
Form 721 (Modelo 721)
Informational return on crypto held in custody abroad, mandatory if the combined balance exceeds €50,000 at December 31.
Declaring ≠ proving.
narrativekey
Executive summary
A 1–2 page document that tells the story (origin, activity, routes and conclusion). The first thing a reviewer reads.
Sets the tone of the dossier.
Template
Response template (ready to send)
Use it as a basis for replying to your bank or exchange, and attach the evidence as annexes. Adapt it to your case; it is a starting point, not a fixed model.
Subject: Proof of crypto holdings and source of funds
1) Ownership. I am the holder of the accounts and wallets and of the associated bank account (KYC and evidence attached).
2) Source of funds. The initial capital comes from __________ (statements and supporting documents attached).
3) Acquisition. I bought crypto-assets on __/__/____ through __________ (deposits and receipts attached).
4) Movements. The funds were moved between __________ for the following reasons: __________ (TxIDs and timeline attached).
5) Sale or conversion. The conversion or sale took place on __/__/____ and the deposit corresponds to __________ (proof of sale and supporting document attached).
6) Taxes. The activity has been or will be declared as appropriate (calculation attached where applicable).
I remain at your disposal to provide further information or additional documentation.
Tell us about your case
Tell us your situation (sale and deposit, Tax Agency information request, exchange review, DeFi or self-custody) and what you have been asked for. We will tell you what evidence to gather and how to build the dossier.
Proving your crypto: source of funds and documentation
Proving the origin of your crypto means demonstrating, with verifiable evidence, the origin, path and destination of the funds in crypto-asset transactions. It is necessary when banks, exchanges, the Tax Agency, notaries or auditors request documentation on where the capital came from, and it always rests on the same chain: fiat source → purchase → movements → sale → deposit.
The dossier should include the fiat source, proof of purchase, exchange history (CSV), on-chain traceability with TxIDs and addresses, proof of sale or conversion, staking or airdrop income if applicable, an executive summary and tax support. For activity involving DeFi, bridges or self-custody, a dedicated traceability report is highly recommended.
Proving and declaring: the tax connection
Declaring and proving are different but complementary. Gains are taxed under personal income tax (IRPF); Form 721 applies to crypto held in custody abroad when the combined balance exceeds €50,000 at December 31; and the EU is extending information exchange through the DAC8 directive. See also Tax Agency audits of crypto and banking crypto proceeds.
Official sources
You can find official information on reporting crypto held abroad from the Spanish Tax Agency (Form 721). This page is for information only and does not constitute legal or tax advice; each case must be analyzed individually.
Crypto and traceability
Tax and information requests
Compliance and AML
Official sources
Key legislation, linked to the official text:
- Law 10/2010 of April 28 on the prevention of money laundering and terrorist financingBOE · consolidated text
- Royal Decree 304/2014 of May 5 approving the Regulation of Law 10/2010 of April 28 on the prevention of money laundering and terrorist financingBOE · consolidated text
Legislation and links reviewed in .