If you’re wondering why you got a random ACH deposit, the short answer is that it almost always comes from one of four places: a government agency (most often the IRS or Social Security), an employer, an insurance company, or your own bank. A smaller share of surprise deposits are processing errors that routed someone else’s money into your account, and a smaller share still are the opening move of a scam. Before you spend a dollar of it, identify the sender.
Read the Deposit Line First
ACH stands for Automated Clearing House, the network banks use to move electronic payments in batches. Every ACH credit on your statement carries a short code and a sender name, and those two fields usually tell you what the money is.
The code you’ll see most often on a personal account is PPD (Prearranged Payment and Deposit), which covers direct-deposit paychecks, government benefits, and recurring personal payments.1Payments Innovation Alliance. ACH File Details Your bank may add its own tag like “ACH DEP” or “DIRECT DEP” next to it. The name field — even when abbreviated — is your best clue to the sender.
The Likely Sources
The IRS
Tax refunds, adjustments, and certain credits from the IRS show up as “IRS TREAS 310” with “TAX REF” in the description. If you see “449” instead of “310,” part of the refund was taken to cover a delinquent debt such as unpaid student loans or back child support.2Bureau of the Fiscal Service, U.S. Department of the Treasury. Tax Refund Frequently Asked Questions Federal payments, including refunds, ride the PPD format.3TFX – Treasury. A Guide to Federal Government ACH Payments If you filed an amended return or claimed a credit months ago and forgot about it, that’s often the explanation.
Social Security
Retirement, disability, and survivor benefits are paid electronically by law.4Social Security Administration. Direct Deposit Payment day tracks the recipient’s birth date: the second Wednesday of the month for birthdays on the 1st through 10th, the third Wednesday for the 11th through 20th, and the fourth Wednesday for the 21st through 31st.5Social Security Administration. Schedule of Social Security Benefit Payments 2025 If the deposit landed on the Wednesday that matches your birth date range, that’s a strong hint.
An Employer
Employers use ACH for paychecks, expense reimbursements, and bonuses. A surprise deposit from an employer is often a retroactive pay adjustment, a reimbursement you filed weeks earlier, or a final paycheck from a job you already left. The company or its payroll processor will show up in the sender name.
An Insurance Company
Claim settlements, health-plan reimbursements, annuity payments, and life insurance benefits all move by ACH. The sender name is sometimes an abbreviation you won’t recognize at a glance, so cross-check the company identification number with your insurer if the name isn’t clear.
Your Own Bank
Banks post interest, promotional bonuses for new accounts, and refunds of fees they charged in error. Promotional bonuses often condition payout on hitting a minimum balance or setting up direct deposit, so the credit can arrive weeks after you stopped watching for it. These entries usually include the bank’s name or a “PROMO” label.
When It’s a Processing Error
The ACH network matches transactions by account number, not by the name on the account. A single wrong digit typed by a payroll clerk or bookkeeper can send someone else’s money into your account, and those errors are most common when a company is setting up a new payee or switching banks.
Software glitches also produce duplicate credits: the same payment file uploaded twice, an old transaction reposted after a system update. In each of these cases the money shows in your balance but doesn’t belong to you, and the sender’s bank has a window to pull it back automatically.
When It’s a Scam
Criminals use ACH deposits to move stolen funds through innocent people’s accounts, a pattern the FBI calls a money mule scheme. It typically starts with a fake job offer, an online relationship, or an unsolicited payment, followed by a request to forward the money somewhere else.6FBI. Money Mules
Watch for these patterns:
- A “work-from-home” arrangement that asks you to accept deposits into your personal account and forward the funds, keeping a percentage.
- A dating-site or social-media contact who wants to route money through your account.
- An “overpayment” where a sender asks you to wire back the difference, buy gift cards, or send cryptocurrency — after which the original ACH deposit is reversed and you’re out the amount you sent.
A legitimate employer will not ask you to process payments through your personal bank account.6FBI. Money Mules If anyone contacts you about an unexpected deposit and asks you to move the money onward, don’t. Report it to your bank and file a complaint at ic3.gov.
How to Identify the Sender
Start with your own records. Recent tax filings, insurance claims, employer emails, class-action notices, and any account with direct deposit set up — most “mystery” deposits turn out to be something you initiated and forgot.
If the sender name still doesn’t ring a bell, call your bank and ask for two things:
- The ACH trace number, a 15-digit identifier assigned to every entry that tracks the payment from the sending bank to yours.1Payments Innovation Alliance. ACH File Details
- The company identification number, a 10-digit code in the batch header that identifies the organization that originated the payment.
Together those two numbers let the bank pin down exactly who sent the money and when. If you suspect an IRS refund, you can also check status through the “Where’s My Refund?” tool or call 800-829-1040.2Bureau of the Fiscal Service, U.S. Department of the Treasury. Tax Refund Frequently Asked Questions
Until you have an answer, leave the money alone. If the deposit was a mistake, your bank can reverse it, and if you’ve spent the funds by then, the reversal can push your balance negative and trigger fees.
What Happens If You Spend Money That Isn’t Yours
Under the doctrine of unjust enrichment, a mistaken transfer doesn’t give you ownership. The sender keeps the right to get the money back and can sue you in civil court to recover it, potentially with interest and legal costs.
Most states also make it a crime to keep property you know was delivered by mistake if you don’t try to return it. The charge may be called theft, larceny, or conversion depending on the state, and the amount involved generally drives whether it’s a misdemeanor or a felony.
Erroneous IRS refunds carry their own consequences. If you don’t return one, the IRS can treat the amount as taxable income for the year you received it.7Internal Revenue Service. 21.4.5 Erroneous Refunds To return an erroneous direct-deposit refund, contact your bank’s ACH department and ask them to send the funds back to the IRS, then call 800-829-1040 to explain. Interest can accrue on the refund until it’s repaid.8Internal Revenue Service. Topic No. 161 – Returning an Erroneous Refund
There’s a bank-side risk too. When your bank reverses an erroneous deposit, it debits the full amount from your account. If the money is already gone, you may face overdraft fees, and if the bank’s fraud system flags the deposit as suspicious, it may freeze the account entirely, cutting off access to funds that legitimately belong to you.
Reversal Timelines You Should Know
On the sender’s side, NACHA rules give the originating bank five banking days after the settlement date of an erroneous entry to transmit a reversal.9Nacha. ACH Network Rules – Reversals and Enforcement After that window closes, the sender generally has to contact you or your bank and request a voluntary return. That five-day clock is why speed matters: report an unfamiliar deposit quickly and the reversal usually happens through normal ACH channels.
On your side, Regulation E requires your bank to investigate a reported error within 10 business days and report the results to you within three business days after it finishes. If it needs more time, it can extend the investigation up to 45 days, but only if it provisionally credits your account within the first 10 business days.10Consumer Financial Protection Bureau. 12 CFR 1005.11 – Procedures for Resolving Errors
Federal agencies have a longer reach. The Social Security Administration, for instance, can reclaim benefit payments made after a recipient’s death: it has 120 days from learning of the death to send a reclamation notice to the bank, and Treasury can then submit the debit to recover the funds for up to three years after that notice.11Social Security Administration. Overview of the Reclamation Process for Title II and Title XVI Electronic Funds Transfer Payments Banks that receive reclamation notices must return the funds if the money is still in the account.
Once you’ve identified the sender and confirmed the deposit is yours to keep, you’re done. If it isn’t, tell your bank in writing, leave the balance untouched, and let the reversal run its course.