A random ACH deposit in your account almost always traces back to a government agency, an employer, an insurance company, or a refund or settlement administrator sending money you either forgot about or didn’t know was coming. Occasionally it’s a bank error, and in a smaller number of cases it’s the opening move of a scam. Until you know which, leave the money where it is. If your bank pulls it back and you’ve already spent it, you’ll owe the difference.
Who Usually Sends These Deposits
Government agencies are behind most surprise credits. The IRS pays refunds and post-filing adjustments by direct deposit, and roughly eight out of ten taxpayers get their refunds that way.1Internal Revenue Service. Direct Deposit Fastest Way to Receive Federal Tax Refund If the IRS corrects an earlier return in your favor or finishes processing an amended one, the credit can arrive months later with no warning. The Social Security Administration also pays retirement, disability, survivor, and SSI benefits electronically, and federal law requires it.2Social Security Administration. Direct Deposit A higher-than-usual Social Security payment often reflects a cost-of-living adjustment or a retroactive correction for prior months.
Employers are the next likely source. Payroll runs are predictable, but bonuses, expense reimbursements, back-pay from an audit, or a final check after leaving a job can land without much context in your transaction history. Insurance companies pay claims the same way, sometimes weeks after you filed the paperwork and stopped watching for it.
Merchant refunds surprise people more often than they should. A return you processed online might refund several business days later under a description that looks nothing like the store name. Class action settlements work similarly: if you filed a claim or were automatically included in the class, the payment arrives from a settlement administrator you won’t recognize. Loan disbursements from online lenders can also appear as ACH credits once the paperwork finalizes.
How to Trace Where the Deposit Came From
The fastest way to identify the sender is to open the transaction in your banking app and read the full description. That short string is the deposit’s fingerprint. Federal tax payments show up as “IRS TREAS 310” followed by a code identifying the payment type: “TAX REF” for a refund from a filed or amended return, “TAXEIP3” for a stimulus payment, and “CHILDCTC” for an advance child tax credit payment.3Taxpayer Advocate Service. TAS Tax Tip – Got a Direct Deposit From the IRS, But Not Sure What It Is For Social Security deposits typically include “SSA” in the description.
Every ACH entry also carries a 15-digit trace number that identifies the specific transfer and a 10-digit Company Identification number that identifies the originator.4Nacha. ACH File Details Your bank’s customer service team can look up both and tell you the electronic path the money traveled. Having those numbers written down before you call saves considerable time.
You may also see a three-letter Standard Entry Class code attached to the transaction. “PPD” is a pre-arranged consumer payment, the kind used for payroll and recurring government benefits. “CCD” signals a business-to-business transfer, common for vendor payments. “WEB” means the transaction started online or through a mobile device, common for person-to-person transfers.4Nacha. ACH File Details Those codes narrow the category of sender before you ever pick up the phone.
For IRS deposits, the “Where’s My Refund?” tool on IRS.gov tracks status through three stages: return received, refund approved, and refund sent.1Internal Revenue Service. Direct Deposit Fastest Way to Receive Federal Tax Refund If your deposit matches an entry there, you’re done.
When a Mystery Deposit Might Be a Scam
Not every unexpected credit is harmless. Two scam patterns are worth knowing about because both start with money appearing in your account without warning.
The first is a money mule scheme. Criminals deposit funds (typically proceeds from fraud) into your account and then ask you to forward the money elsewhere through a wire transfer, a payment app, or a money service. Recruitment often comes through what looks like a work-from-home job or through someone contacting you on a dating site. The FBI describes the pattern: being asked to open an account to receive and transfer funds, being told to “process” payments through your personal account, and being allowed to keep a cut of what you move.5Federal Bureau of Investigation. Money Mules People caught in these schemes face serious federal exposure, including fines up to $500,000 and up to twenty years in prison for money laundering.6Office of the Law Revision Counsel. 18 U.S. Code 1956 – Laundering of Monetary Instruments
The second pattern is simpler. A scammer sends you money, often from a stolen account or compromised card, then contacts you claiming the transfer was an accident and asks you to return it through Zelle, Venmo, a gift card, or a wire. If you send the money back that way, the original fraudulent deposit eventually gets reversed by the real account holder’s bank, and the funds you moved through the non-reversible channel are gone. The FTC treats any request to return money through gift cards, cryptocurrency, wire transfers, or payment apps as a red flag.7Federal Trade Commission. Refund and Recovery Scams
If someone contacts you about an “accidental” deposit and pressures you to send it back any way other than letting the banks handle the reversal, don’t. Report it to your bank and file a complaint with the FTC or the FBI’s Internet Crime Complaint Center.
What to Do, in Order
- Leave the money alone. Don’t move it, don’t spend it, don’t transfer it. If the deposit turns out to be an error, the originating bank can reverse it automatically. If the balance isn’t there, your account goes negative.
- Check your own records first. Recent tax filings, insurance claims, employer messages, class action notices, and online returns explain the majority of these deposits.
- Call your bank. Ask them to look up the trace number and Company ID and trace the payment back to the originating institution. Keep a log of when you called, who you spoke with, and any reference numbers.
- Report suspected fraud. If anyone has contacted you asking for the money back, tell your bank right away and file a report with the FBI’s IC3 or the FTC.
The burden of figuring this out sits with the banks, not you. Your job is to report the discrepancy, leave the money untouched, and document what you did.
How ACH Reversals Work
When a company or agency sends money to the wrong person, its bank can initiate a reversing entry. Under Nacha’s operating rules, that reversal has to reach your bank within five banking days of the original deposit’s settlement date. The permitted reasons are narrow: a duplicate payment, an incorrect recipient, a wrong dollar amount, and certain timing errors.8Nacha. ACH Network Rules – Reversals and Enforcement
A legitimate reversal happens automatically. Your bank debits the amount without asking you first. If you’ve spent the money and your balance won’t cover the debit, you end up with a negative balance, overdraft fees, and a debt to your bank. That’s the single most common way people get hurt by an unexpected deposit.
Your bank can also block an improper reversal. If the reversal is initiated for a reason not permitted under the rules or after the five-day window, your bank can return it on your behalf. For consumer accounts, the bank needs your written statement that the debit was unauthorized, and the return must happen within 60 calendar days of the improper reversal’s settlement date.8Nacha. ACH Network Rules – Reversals and Enforcement
Why You Can’t Just Keep the Money
There’s a persistent myth that money landing in your account is yours. It isn’t. The legal principle of unjust enrichment requires you to return funds you have no legitimate claim to, and banks enforce this mechanically by debiting the account to recover an erroneous deposit regardless of your current balance. Spend the money and you owe the bank.
Knowingly spending money that was deposited by mistake can also bring criminal charges for theft. The specific charge and severity vary by state, with felony thresholds ranging from roughly $500 to $2,500 depending on the jurisdiction, but the underlying pattern is consistent: spending money you know isn’t yours qualifies as theft even if it arrived uninvited. Civil suits from the originating party are also possible.
The risk climbs sharply when the deposit is connected to fraud. Moving money for someone else as a mule can trigger federal money laundering charges carrying fines up to $500,000 and up to 20 years in prison, even if you didn’t understand the full scheme.6Office of the Law Revision Counsel. 18 U.S. Code 1956 – Laundering of Monetary Instruments The FBI notes that even people recruited through fake job offers or online relationships, who don’t realize the funds are stolen, still face prosecution.5Federal Bureau of Investigation. Money Mules
The safest response never changes. Leave the deposit alone, report it to your bank, and let the institutions sort it out. If anyone is pressuring you to move the funds or threatening you over money you didn’t ask for, talk to a lawyer before you do anything else.