Chemicals in a stolen check can rewrite who gets paid and how much

A stolen paper check does not need to be forged from scratch to become dangerous. Criminals can simply alter one with chemicals, wiping out the original payee’s name and dollar amount and writing in new ones, according to a Federal Bureau of Investigation and Internet Crime Complaint Center public service announcement. The tactic, known as check washing, turns a routine piece of mail into a blank instrument the moment it leaves a mailbox.

A second method skips the chemicals entirely and edits a digital photo of the check instead.

Two ways a stolen check gets rewritten

IC3’s PSA draws a clear line between the two techniques circulating today. Check washing “involves the use of chemicals to physically alter the check, typically altering the original payee and financial amount,” erasing the ink a bank would otherwise treat as final. Check cooking is the newer variant: it “involves the digital manipulation of an image of a stolen check,” using ordinary photo-editing software and a high-quality printer to manufacture a check that never touched a chemical bath at all. The bureau’s PSA, published Jan. 27, 2025, treats the two techniques as related but distinct problems for banks trying to catch altered items before they clear.

Both versions end at the same place — a check that clears through a bank’s normal processing, at least until the original account holder or business notices the mismatch between what was written and what was cashed.

The pull of blue collection boxes

IC3 traces much of the supply of stolen checks to a specific and predictable weak point: USPS blue collection boxes theft occurring “after the last pickup time,” when mail deposited during the day sits exposed overnight before the next scheduled collection. A single box can hold dozens of envelopes, some containing rent payments, tax refunds or business checks, making it a higher-value target than any individual mailbox at a house.

Financial crime investigators have watched that supply chain scale into a distinct fraud economy. Once a check is pulled from a box, it can be washed or cooked, then deposited or sold to a network of people recruited to cash altered checks for a cut of the proceeds — a division of labor that spreads the fraud across more participants and more banks than a single thief acting alone could manage.

The paper trail behind the surge

The trend shows up clearly in the Suspicious Activity Reports banks are required to file. The Treasury Department’s Financial Crimes Enforcement Network reported that financial institutions filed more than 350,000 check fraud-related SARs in 2021, then more than 680,000 in 2022 — nearly double in a single year. IC3’s own PSA describes a similar pattern, noting that check fraud-related reports “nearly doubled” between 2021 and 2023.

FinCEN issued its alert jointly with the U.S. Postal Inspection Service in February 2023, and Acting Director Himamauli Das framed it as an interagency response to the number of reports piling up: “FinCEN is proud to partner with the United States Postal Inspection Service in producing this important and timely alert on mail theft-related check fraud designed to assist financial institutions in reversing this disturbing trend.” The alert names personal checks, business checks, tax refunds and government assistance payments as the categories investigators see stolen most often.

Cashing a washed check is not a minor offense once it reaches a courtroom. Bank fraud carries penalties of up to $1 million in fines or 30 years in prison under federal law, a scale investigators cite to distinguish check washing from a low-stakes forgery case.

Cutting the odds of a washed check

The Postal Inspection Service’s check-fraud guidance centers on a handful of low-effort habits. Writing checks in indelible black ink makes the payee and amount harder to lift chemically than checks written in ballpoint or gel pens that wash more easily. Leaving no blank space on the payee or amount line closes off the room a washer needs to insert new characters, and keeping a Social Security number, driver’s license number or account details off the paper entirely limits what a stolen check can be used for beyond a single fraudulent deposit.

Monitoring cleared checks through mobile or online banking, rather than waiting for a paper statement, is the fastest way account holders spot an altered payee or amount before the loss compounds. USPIS also recommends routing outgoing checks through a Postal Service counter or the letter slots inside a post office instead of a blue collection box, and switching to electronic payments such as ACH transfers where the payee accepts them, since a check that never becomes paper cannot be washed.

Suspected mail theft or fraudulent check activity can be reported directly to the Postal Inspection Service, which coordinates with FinCEN and the banks that filed the underlying suspicious-activity reports behind the 2021-to-2022 doubling.

This article was produced with the assistance of AI and reviewed by Morning Overview editors prior to publication.