Yes, it is illegal to keep money someone sent you by accident once you know the transfer was a mistake. The law treats those funds the way it treats a wallet you found on the sidewalk: the money still belongs to the sender, and holding onto it, spending it, or moving it can expose you to a civil lawsuit for the full amount plus legal costs, and in many cases to criminal theft charges.
It doesn’t matter how the money arrived. A misrouted Zelle payment, a bank that credited someone else’s deposit to your account, a company that overpaid you, a stranger who typed the wrong phone number into Venmo — the rule is the same. You didn’t ask for it, you may not have noticed it, and you did nothing wrong by receiving it. Your obligation to return it kicks in the moment you realize it wasn’t meant for you.
Why the Money Isn’t Legally Yours
The underlying principle is called unjust enrichment. If you receive a benefit at someone else’s expense with no legitimate reason to keep it, the law says you owe it back. Courts apply this broadly: the source of the error — the sender, a bank’s internal system, a payment app glitch — doesn’t change who the money belongs to. You’re essentially holding it in trust until it’s returned.
This is why “finders keepers” instincts don’t translate to money that lands in your account. A deposit isn’t a gift unless someone meant to give it to you. If no one did, you are closer to a courier than an owner.
Civil Lawsuits for Refusing to Give It Back
If you won’t return the money voluntarily, the sender can sue you. The two usual claims are unjust enrichment and conversion. Conversion is the civil equivalent of theft: intentionally exercising control over property that belongs to someone else. For conversion, the sender doesn’t even have to prove you knew the money wasn’t yours when it arrived. They only have to show you treated it as your own.
If a court rules against you, the order will require you to return the full amount, and may add the sender’s legal costs and attorney’s fees. You can end up paying back more than you received. The statute of limitations varies by jurisdiction but typically runs two to four years, so the sender has time to come after you even if nothing happens right away.
When Keeping the Money Becomes a Crime
The line between a civil dispute and a criminal case is intent. Receiving money by mistake isn’t a crime. The crime is knowing the money isn’t yours and deliberately keeping or spending it. Most states classify this as a form of theft, sometimes called theft of property lost by mistake or theft by finding.
Prosecutors look at what you did after the money arrived. Did you move it to a different account? Spend it? Ignore calls and letters from the bank asking for it back? Any of those steps suggests you meant to permanently deprive the rightful owner, which is the mental state a theft conviction requires.
Penalties scale with the amount. Most states draw the felony line somewhere between $750 and $2,500. Below that, you are generally looking at a misdemeanor, with fines and up to a year in jail. Above it, prison sentences can run several years depending on the amount and the state. In one widely reported case, an 18-year-old who went on a spending spree with $31,000 that was deposited into his account by error was sentenced to ten years of probation. A recipient in another case was charged with a third-degree felony for similar conduct. These are not hypothetical risks.
What to Do the Moment You Notice It
Leave the money alone. Don’t spend it, don’t transfer it to savings, don’t invest it, don’t send it anywhere. Keeping the funds untouched where they landed is the clearest evidence that you never intended to keep them. Every dollar you move creates a potential legal problem, because even if you plan to pay it back later, you’ve exercised control over someone else’s property.
Then contact your bank or payment provider. Give them the transaction details and tell them you believe the funds were sent to you in error. This starts the institution’s formal error-resolution process and creates a timestamped record showing you acted in good faith. For electronic transfers, federal Regulation E treats an incorrect electronic fund transfer as a defined error that triggers the bank’s investigation duties.1Consumer Financial Protection Bureau. 12 CFR 1005.11 – Procedures for Resolving Errors
One important thing to know: once a bank opens an investigation, it has the authority to reverse the transaction and pull the money back out of your account. It doesn’t need your permission and may not give you much warning. That is a feature of the system, not a problem — it’s the mechanism that gets the money back where it belongs without you having to do anything.
Don’t Send the Money Back Yourself
If the sender contacts you directly through a payment app and asks you to return the money, be careful. This is the setup for one of the most common payment-app scams.
Here’s how it works. A scammer sends you money, then messages you claiming it was a mistake and asks you to send it back. The catch is that the original payment was funded with a stolen credit card or a compromised bank account. When the real account holder spots the fraud and disputes the charge, the platform claws the original payment back out of your account. The money you “returned” is already gone, sent to a different account the scammer controls. You end up out of pocket for the full amount.
So never send money back directly, even when the request sounds reasonable. Tell the person to contact their own bank or payment provider and request a formal reversal. If the payment was genuinely a mistake, the reversal will come through normal channels and both of you are protected. If it was a scam, you’ve just dodged it. Route everything through the financial institution, and keep screenshots of any messages you receive.
If You Already Spent It
This is where people get into the most trouble. An unexpected deposit shows up, you assume it’s a refund or bonus you forgot about, and you spend it before anyone reaches out. Spending the money does not erase your obligation to return it. The bank can still reverse the transaction, and if your balance can’t cover the reversal, you end up negative. The bank may then pursue you through collections for the deficiency.
If you’ve already spent mistaken funds and the bank or sender contacts you, the worst move is going silent. Call the bank, explain what happened, and ask about repayment options. Many banks will work out a payment plan rather than escalate, especially if you cooperate and the amount isn’t huge. What turns a recoverable mistake into a criminal matter is the appearance that you knew the money wasn’t yours and tried to keep it anyway. Showing good faith, even late, is your best protection.
Side Effects People Don’t Expect
Your Account May Get Frozen
When a bank investigates a reported erroneous transfer, it can temporarily restrict access to your account — not just the disputed funds, but potentially the entire balance. Federal law doesn’t impose a specific time limit on freezes during a fraud or error investigation, though courts generally require the duration to be reasonable and tied to a legitimate investigative purpose.
Under Regulation E, the bank has ten business days to complete its investigation, extendable to 45 days if it provisionally credits the complaining consumer’s account.1Consumer Financial Protection Bureau. 12 CFR 1005.11 – Procedures for Resolving Errors During that window your access to your own money could be limited. If autopay bills run through the account, a freeze can snowball into late fees, missed payments, and credit reporting problems that have nothing to do with the original error. Notifying your bank fast and cooperating with the investigation is the best way to keep any restrictions short.
You May Get a 1099-K for Money That Wasn’t Yours
If the mistaken transfer came through a payment platform, you might receive a Form 1099-K that reports the amount as income, even though it was an error. Payment processors have to report transactions above certain thresholds to the IRS, and their systems generally can’t tell a real payment from an accidental one.
If this happens, the IRS says to contact the form’s issuer right away and ask for a corrected version. If the issuer won’t fix it, you can zero out the impact on your return by reporting the amount on Schedule 1 (Form 1040) as “Other Income — Form 1099-K Received in Error” on Line 8z, and entering an equal offsetting adjustment on Line 24z. The net effect on adjusted gross income is zero.2Internal Revenue Service. Actions to Take if a Form 1099-K Is Received in Error or With Incorrect Information Keep records of the original error and your efforts to return the money, because if the IRS questions the adjustment, you’ll need to show the payment was never actually income.