What Is a Source of Funds Check When Withdrawing Crypto to a Bank?

13 October 2026

A source of funds check is a routine compliance procedure where a bank or crypto exchange asks you to prove where the money you are withdrawing originally came from. It is a legal requirement designed to prevent money laundering, fraud, and other financial crimes. When you request a large withdrawal from a crypto exchange to your linked bank account, the platform may pause the transaction and request documentation showing the legitimate origin of the funds you are moving.

Why Do Exchanges and Banks Perform Source of Funds Checks?

Financial institutions are legally obligated to verify the origin of money that passes through their systems. Anti-money laundering (AML) regulations require them to identify suspicious activity. A large or sudden crypto withdrawal can look unusual on a bank’s radar, so the exchange or bank will ask for proof that the funds came from a legitimate source - not from illegal activity like scams, ransomware, or drug sales.

The check is not a personal accusation. It is a standard, automated compliance step triggered by thresholds, patterns, or jurisdiction-specific rules. For example, withdrawals above a certain amount (often around $10,000 equivalent in many countries, but exact amounts vary by institution) are more likely to trigger a review.

What Triggers a Source of Funds Check?

Several factors can prompt a check:

• Withdrawal size: Large amounts relative to your account history or typical user behavior.
• Account age: New accounts moving significant sums quickly.
• Transaction patterns: Frequent deposits and withdrawals, or rapid trading before a withdrawal.
• Bank policies: Some banks are stricter than others about crypto-related transfers.
• Jurisdiction: South Korea, for example, has specific reporting requirements for crypto transactions above certain thresholds.

The exact triggers are not public - exchanges and banks keep their risk models secret to avoid being gamed.

What documents are typically requested?

You may be asked to provide one or more of the following:

• Bank statements showing the original deposit of funds used to buy crypto.
• Proof of income such as pay slips, tax returns, or business revenue records.
• Trading history from the exchange showing how the crypto was acquired and held.
• Screenshots of transactions showing the purchase price and timing.
• A written explanation of how the funds were obtained.

The documents must usually show a clear chain from your original fiat deposit to the crypto purchase, through any trading, and finally to the withdrawal request.

How to Prepare for a Source of Funds Check

You cannot avoid the check if it is triggered, but you can make it less painful by keeping records:

1. Save deposit records: When you first buy crypto with fiat, keep the bank statement showing the deposit to the exchange.
2. Maintain trading logs: If you trade frequently, keep a record of each trade (date, amount, pair, fees).
3. Use a single exchange when possible: Moving crypto between multiple exchanges can complicate the paper trail.
4. Be honest: Fabricated documents will be detected and can result in account closure or legal action.

What happens during the check?

The process usually goes like this:

1. You initiate a withdrawal.
2. The exchange holds the transaction and contacts you via email or in-app message requesting documents.
3. You upload the requested files through a secure portal.
4. The exchange reviews them. This can take anywhere from a few hours to several business days, depending on the complexity and the exchange’s staffing.
5. If approved, the withdrawal proceeds. If denied, you may be asked for more documents or the withdrawal may be refused entirely.

How to Respond If You Are Asked for a Source of Funds Check

• Do not ignore it: The request will have a deadline. Missing it can result in the withdrawal being canceled or your account being restricted.
• Provide exactly what is asked: Do not send extra documents unless they clarify a gap. More is not always better.
• Keep copies: Save your submission for your own records.
• Contact support if unclear: If the request is vague, ask for specific examples of acceptable documents.

Can a Source of Funds Check Be Avoided?

Not if you are dealing with regulated institutions. However, you can reduce the likelihood by:

• Withdrawing smaller amounts over time rather than one large sum.
• Using an exchange where you have a long, consistent history.
• Keeping your account activity predictable.

But these steps are not guarantees. The check exists because the law requires it, not because the exchange wants to inconvenience you.

What if you cannot provide the documents?

If you cannot prove the source of funds, the withdrawal will likely be rejected, and your account may be suspended or closed. The exchange is legally required to report suspicious transactions to financial authorities. In serious cases, your bank may also freeze the linked account and report the activity.

Key Takeaway

A source of funds check is a standard, legal requirement for moving large sums of crypto into a bank account. It is not personal. The best defense is to keep clear records of how you acquired your crypto from the moment you deposited fiat money. If the check comes, respond promptly and honestly with the requested documents.

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