Reviewed September 2026.
Check washing is mail theft plus forgery: someone steals an outgoing check from a mailbox or USPS blue box, uses chemicals to erase the payee name and amount, then rewrites the check to themselves or a mule. The routing and account numbers at the bottom stay readable, so the thief can also build counterfeit checks. Related job/check fraud: Fake job and check-cashing scams.
How the crime works
- Thief watches for raised flags or fishes blue collection boxes.
- Stolen check is washed (solvents remove many ballpoint inks).
- New payee and higher amount are written in.
- Check is deposited via mobile deposit or a cooperating cashier.
- Your bank statement shows a cleared check you do not recognize; meanwhile the real landlord or utility never got paid.
USPS and bank trade groups have warned about spikes in check theft along collection routes. Paper checks in residential boxes remain a soft target compared with confirmed electronic / ACH payments (not every “bill pay” product stops mailing paper).
Prevention that actually changes the odds
| Move | Detail |
|---|---|
| Prefer electronic pay | ACH / direct electronic payment when the biller and bank confirm the payment is not mailed as a paper check. Some “online bill pay” products still print and mail a check. Ask before you assume mail-theft exposure ended (Bill pay without late fees) |
| If you must mail a check | Use a locked outgoing slot or hand it to a clerk inside the post office; avoid overnight street boxes when possible |
| Ink | Use a gel pen or other check-safe ink that resists washing better than cheap ballpoint (still not perfect) |
| Mailbox | Locked cluster box or slot that blocks fishing; bring incoming mail in daily |
| Bank alerts | Turn on alerts for checks clearing over a dollar threshold you choose |
| Positive pay / carve-outs | Small-business accounts may offer payee match; ask your bank |
| Limit leftover checks | Shred voided checks; do not post photos of checks that show the MICR line |
A stolen wallet with a checkbook is a cousin problem: Stolen wallet financial checklist.
Worked example: $2,850 washed rent check
Nina mails rent ($1,950) from her residential mailbox with the flag raised. Two weeks later her bank shows check #4412 cleared for $2,850 to a name she does not recognize. Her landlord texts that rent never arrived.
- Nina calls the bank fraud line from her statement; asks to stop payment on any unused checks and to dispute #4412 as altered.
- She files a USPS / Postal Inspection Service mail-theft report and identifies the residential mailbox where she mailed the check (not a blue-box location she did not use).
- She pays the landlord electronically the same day so she is not also in breach of lease.
- She files ReportFraud.ftc.gov and follows Report a scam to the FTC and your bank.
- She switches future rent to ACH / confirmed electronic bank bill pay (asks the bank whether payments are mailed as paper checks) and shreds remaining paper checks after the bank ships a new account number (if the bank recommends renumbering).
If a washed or forged check already cleared
- Contact the bank immediately; ask about altered-check claims and whether the account number should change.
- Review the last 60–90 days for other forged items; consider unauthorized ACH pulls that reuse the MICR data.
- File a USPS Inspection Service complaint for mail theft.
- Tell the intended payee you will repay through a safer rail; keep proof.
- Monitor the account daily for two weeks; turn on real-time alerts.
Checklist
- Move recurring bills to ACH or confirmed electronic bank bill pay where the biller allows it; ask whether the bank still mails a paper check.
- Stop leaving outbound checks in unsecured residential boxes overnight.
- Use check-resistant ink; treat the MICR line as a secret.
- Enable clearance alerts; dispute altered checks the same day you see them.
- Report mail theft through official USPS channels and your bank fraud desk.
Educational only. Not legal advice. Bank altered-check rules and USPS reporting steps vary; use your bank’s official fraud process and USPS.com / USPIS channels for current forms.