# Check Washing: How Mailed Checks Get Rewritten

- Author: PreciseBankFlow (https://www.precisebankflow.com)
- Published: 2026-06-22
- Updated: 2026-06-22
- Category: Embezzlement and fraud schemes
- Canonical: https://www.precisebankflow.com/blog/check-washing

> How check washing rewrites stolen mailed checks, how it appears on the statement and reconciliation, and the controls that cut the risk.
Check washing is a fraud in which a thief steals a mailed check, dissolves the ink with chemicals, writes in a new payee and often a larger amount, then deposits it. For the business that wrote the check, the loss surfaces later: a cleared check that matches the register's number but not its payee or amount.

## How does check washing rewrite a stolen check?

Check washing starts with mail theft. Checks are taken from collection boxes, office mail trays or residential mailboxes, the ink on the payee and amount lines is removed with chemicals, and the thief writes new details over the original signature. The altered check is then deposited or cashed before the writer notices anything.

FinCEN's [February 2023 alert on mail theft-related check fraud](https://www.fincen.gov/sites/default/files/shared/FinCEN%20Alert%20Mail%20Theft-Related%20Check%20Fraud%20FINAL%20508.pdf) describes the pattern. Stolen checks are washed to replace the payee, often with an increased amount, and sometimes copied and sold to other criminals. The alert notes that business checks can be worth more to thieves because business accounts are often well funded and it may take longer for the victim to notice.

Once rewritten, the check usually goes into an account opened for the purpose, or one belonging to a money mule. It may be deposited at a branch, an ATM or by mobile capture, and the funds are withdrawn or moved quickly. The signature is real, which is why a washed check can pass through the bank's normal processing.

The [US Postal Inspection Service's check washing guidance](https://www.uspis.gov/news/scam-article/check-washing) names a common first sign: a check you sent was cashed, but the person it was meant for says it never arrived.

## Washed checks on the bank statement and the reconciliation

A washed check clears under its original check number, so on a bank reconciliation it looks like a routine outstanding check that finally cleared. The difference is in the details. The amount may not match the register, and the check image shows a payee you never wrote. A reconciliation that only ticks check numbers will miss it.

The comparison below is an example of what a washed check looks like against the check register. The figures are illustrative.

| Field | Check register | Cleared check image |
| --- | --- | --- |
| Check number | 4182 | 4182 |
| Date written | 2026-05-04 | 2026-05-04 |
| Payee | Harbor Paper Supply | D. Morrison |
| Amount | 286.40 | 2,860.40 |
| Endorsement | (expected: vendor's deposit stamp) | Mobile deposit, personal account |

Three habits catch this at the reconciliation:

- **Match the amount, not just the number.** A cleared check whose amount differs from the register is never a rounding issue. The steps for that case are in [handling a check that cleared for a different amount](/blog/check-cleared-for-different-amount).
- **Look at the image for large or unusual items.** Payee changes, overwriting and mismatched endorsements are visible on the image, and [the guide to altered check images](/blog/altered-check-images) explains what to look at.
- **Watch for the vendor's reminder.** A past-due notice from a supplier whose check shows as cleared is a washed check until proved otherwise.

When a reconciliation tool matches cleared items to the register on amount as well as number, a washed check shows up as an exception instead of a tick. [PreciseBankFlow](/) lists every unmatched or mismatched line with the statement line beside it, so a reviewer sees the 2,860.40 against the 286.40 without reading every check.

## Which controls cut check washing losses?

The controls that cut check washing losses either stop the check from being stolen, make the alteration harder, or stop the bank from paying a changed check. Payee positive pay does the last of these and is the strongest of the three. Paying suppliers electronically removes the paper check from the mail altogether.

A short control checklist:

1. **Use payee positive pay.** The bank compares the payee name as well as the number and amount against your issued-check file. Plain positive pay without the payee check will pay a washed check whose amount was left alone. [How positive pay works](/blog/what-is-positive-pay) covers the setup.
2. **Mail checks inside a post office**, or in a collection box before the last pickup, as USPIS advises. Do not leave outgoing mail in an office tray or an unlocked box overnight.
3. **Write or print with ink that resists washing**, and use check stock with security features.
4. **Pay regular suppliers by ACH** so fewer checks travel by mail.
5. **Reconcile monthly or more often**, matching amounts and reviewing images for large checks.

Moving to electronic payments brings its own risk: an email asking you to update a supplier's bank account. [Business email compromise payment fraud](/blog/business-email-compromise-payment-fraud) covers that scheme. A [fraud risk assessment](/blog/fraud-risk-assessment) is the place to weigh check fraud against payment diversion and decide which controls your business needs most.

## Check washing found: the vendor who says the payment never arrived

When a vendor says a payment never arrived and the check shows as cleared, treat it as possible check washing. Get the front and back images from the bank, report the altered check to the bank in writing straight away, and pay the vendor again only once you know the original was not deposited by them.

Act in this order:

- **Call the bank's fraud line** and follow up in writing. Your account agreement sets a time limit for reporting altered items, so read it and do not wait for month end.
- **Report the mail theft** to the Postal Inspection Service, which USPIS asks victims to do, and to local police.
- **Stop or check the rest of the batch.** Checks mailed the same day from the same box may also have been taken.
- **Reissue the vendor's payment** electronically if you can, once the bank has the claim.

## When check washing is an inside job

Not every altered check comes from a mail thief. An employee who prepares or mails checks can change a payee or amount, and an employee who submits expense claims can alter a reimbursement check made out to them. The washing technique is the same; the difference is who had the check before it went out.

An inside job tends to leave signs that an outside theft does not. The altered checks cluster around one preparer, the register may have been edited to match the altered amount, and the payee is someone the employee knows. Reimbursement checks altered by the claimant are one form of the wider scheme described in [expense reimbursement fraud](/blog/expense-reimbursement-fraud). Separating who prepares checks from who mails them and who reconciles the account makes this version much harder to hide.