Check Washing: How Criminals Alter Business Checks and How AP Stops It
Check washing is the use of chemicals to erase the ink on a stolen check, usually the payee name and the amount, so a criminal can rewrite it and deposit it. For a business, every check mailed to a vendor is a potential target, carrying a valid account number on its face.
The scale grew fast. Financial institutions filed more than 350,000 check-fraud suspicious activity reports with FinCEN in 2021, up 23%, and over 680,000 in 2022, nearly double, according to FinCEN's February 2023 alert on mail theft-related check fraud. Those are the most recent FinCEN counts available, and nothing since suggests the problem has gone away.
Most of what's written about check washing is aimed at consumers paying a utility bill. AP has a different exposure. It mails more checks, for larger amounts, on a schedule anyone watching a mailbox could learn.
Key Takeaways
Check washing removes the ink on a stolen check so the payee and amount can be rewritten, and most stolen checks are taken from the mail.
Business checks are bigger targets than personal ones, because amounts are larger and every check carries a working account and routing number.
Standard positive pay matches check number and amount, so catching a changed payee name needs payee positive pay.
Secure check stock, careful mailing, and daily exception review reduce the risk, but only issuing fewer checks removes it.
Moving the highest-volume and highest-value vendors to ACH or virtual card first cuts the most exposure for the least effort.
What is check washing?
Check washing is a fraud in which a criminal steals a check, chemically removes the handwritten or printed details, and fills in a new payee and usually a higher amount. The U.S. Postal Inspection Service describes check washing scams as changing the payee names, and often the dollar amounts, on checks and fraudulently depositing them.
FinCEN's alert adds the detail that matters to AP. It describes washing as using chemicals to remove the original ink to replace the payee and often the amount, which washers frequently raise by hundreds or thousands of dollars. It also names where the checks come from, which is USPS blue collection boxes, unsecured residential mailboxes, and privately owned cluster box units.
Washing differs from counterfeiting, though the two often travel together. Washing reuses the original paper with new ink. A counterfeit is a new check printed from the details on a stolen one, which is why a stolen check can be used more than once even after the original is gone.
How does a washed check get cashed?
A washed check moves through the same channels as a legitimate one, which is why it often clears. The usual sequence runs like this:
A thief takes the check from a collection box, a mailbox, or a mail carrier.
Chemicals strip the ink, and a new payee and amount are written in.
The criminal deposits it, often through mobile or remote deposit into an account opened for the purpose.
Once it clears, the funds are withdrawn quickly.
The business discovers the problem at reconciliation, or when the real vendor calls about a missing payment.
Step five is the weak point for most companies. If the account is reconciled monthly, a washed check can sit undetected for weeks, and the vendor's "where's my payment" call is sometimes the first signal anyone gets.
Why are business checks a bigger target?
Business checks are bigger targets because the amounts are larger, the account behind them is funded, and each one hands over a working account and routing number. A washer who steals a household check might gain a few hundred dollars. A vendor payment can be worth far more, and the same account details can be printed onto counterfeit checks afterward.
Timing helps the thief too. Many AP teams run a weekly or biweekly check run and drop the batch in the same collection box on the same day. Mail theft rose sharply during the pandemic. The U.S. Postal Inspection Service received 299,020 mail theft complaints from March 2020 through February 2021, up 161% from a year earlier, according to the same FinCEN alert.
How can banks and AP teams detect a washed check?
The most reliable detection comes from positive pay, where the bank compares each presented check against the issue file the company sent and holds anything that doesn't match. Fast exception decisions and frequent reconciliation do the rest.
The mechanics of positive pay are worth understanding in full, but the short version is that AP sends the bank a list of every check issued, and the bank flags presented items that don't appear on it. Someone at the company then decides, usually by a daily cutoff, whether to pay or return each exception.
That decision step is where programs fail quietly. If exceptions default to "pay" when nobody responds, and the person responsible is out that week, the control does nothing. Set the default to "return," name a backup decision-maker, and the same control becomes much harder to slip past. Corpay's single-use virtual cards avoid the problem for suppliers that accept them, since each card number works for one approved payment.
Does positive pay catch a washed check if the payee name changed?
Standard positive pay usually won't catch a washed check if only the payee changed, because it matches the check number and amount. Catching a rewritten payee name needs payee positive pay, which also compares the payee on the presented check to the issue file.
Two conditions apply. The bank has to offer payee matching, and the account has to be enrolled in it, with the issue file carrying the payee name exactly as printed. Many washers raise the amount as well as the payee, so standard positive pay catches a share of washed checks by accident. Relying on that is a gamble, and a thief who leaves the amount alone gets through. If your bank offers payee positive pay and you're still on the standard service, upgrading is probably the single most useful change in this article.
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How fast do you have to report an altered check?
The deadline for reporting an altered check is set by your deposit account agreement and the rules that apply to it, and it can be short. Read the agreement for each operating account, find the notice window for unauthorized or altered items, and build your reconciliation schedule to beat it.
Daily review of cleared checks, or at least daily positive pay exception review, is the practical answer. Monthly reconciliation finds the problem, but it may find it after the window for recovering the money has narrowed. Who bears the loss is a separate question, and B2B payment fraud liability covers how that tends to fall between banks and businesses.
How do you prevent check washing in accounts payable?
You prevent check washing with layered controls on the check itself, on how it's mailed, and on how fast the bank and AP catch an altered item. No single control is enough:
Enroll every disbursement account in payee positive pay, and default exceptions to return.
Use check stock with security features designed to show tampering, and store it locked, with a log.
Print checks with ink and fonts that resist removal, where your printer supports them.
Mail checks inside a Post Office or in a blue collection box before the last pickup, never in an unattended outgoing box.
Review positive pay exceptions and cleared items daily, and reconcile disbursement accounts at least weekly.
Validate vendor bank details before switching anyone to electronic payment, so the fix doesn't create a new fraud path.
The mailing guidance follows USPIS, which recommends using blue collection boxes before the last pickup or the Post Office counter, collecting mail promptly, and holding mail when you're away. Vendor verification and bank validation covers the last item, which matters because fraudsters target the switch from check to ACH as well.
My position is that these controls lower the risk without removing it. As long as a check exists, it can be stolen, and the only way to take the risk off the table is to stop issuing that check. Corpay pays suppliers by virtual card, ACH, or check from one approval flow, so moving a vendor off paper doesn't mean building a new process.
Will a gel pen or Sharpie prevent check washing?
A gel pen or permanent marker makes washing harder, but it won't prevent check fraud. Pigment-based ink is more resistant to the solvents washers use than ordinary ballpoint ink, so a hand-written check filled in with it is a worse target.
The limits are real, though. Most business checks are printed, not hand-written, so pen choice rarely applies. And a thief who can't wash a check can still use its account and routing numbers to print a counterfeit. Ink is a small help on personal checks and close to irrelevant for a printed AP check run.
What does it cost to keep mailing vendor checks?
Every vendor still paid by check carries a theft and washing risk on every payment, plus the handling cost of printing and mailing paper and then reconciling it. The fraud data shows where that risk concentrates.
Paper checks were the payment method most targeted by fraud in 2025, cited by 58% of organizations, followed by ACH debits at 30% and wire transfers at 25%, according to the 2026 AFP Payments Fraud and Control Survey Report. Checks are also sticky. In the same survey, 72% of organizations using checks plan to keep using them for the foreseeable future, and 68% of those cite vendor requirements as a reason.
The broader payment mix is moving away from paper anyway. US check payments fell to 9.2 billion by number and $24.45 trillion by value in 2024, down 1.8 billion and $1.92 trillion from 2021, according to the Federal Reserve Payments Study. Among business payments specifically, checks fell from 32% of B2B payments by number in 2015 to 13% in 2024, while ACH rose from 25% to 41%, according to a Federal Reserve Bank of Cleveland payments research brief.
The electronic side keeps growing. B2B ACH payments rose 155% from 2.9 billion in 2015 to 7.4 billion in 2024, according to Nacha's coverage of the long-run decline in B2B checks. More recently, B2B payments on the ACH Network reached 2.2 billion in the second quarter of 2026, up 9.9% year over year, according to Nacha's second-quarter 2026 report.
That vendor-requirement figure matches what I've seen. When AP teams look at why a vendor is still on checks, the answer is often that nobody asked. The vendor's AR clerk deposits checks because that's how they've always been paid, and a single enrollment call with a clear explanation of how remittance will arrive moves more vendors than any policy memo. Printing, postage, and the rest of the cost picture are laid out in the true cost of paper checks.
What is the cheapest way to cut check-washing risk?
The cheapest way to cut check-washing risk is to move your highest-volume and highest-value check vendors to electronic payment first. A small share of vendors usually accounts for a large share of check dollars, so a short list of conversions removes most of the exposure.
A short sequence keeps the effort focused:
Sort your last year of check payments by vendor, once by total dollars and once by count.
Call the vendors near the top of either list first, starting with those already paid electronically by other customers.
Confirm new bank details by phone at a number you already have on file before the first electronic payment.
Keep the vendors who refuse on checks, with payee positive pay, and revisit them at contract renewal.
Some will take ACH credits, where you push the payment and control the timing. Others already accept cards and can be paid with single-use cards, which expire after one payment and leave nothing worth stealing. The checks that remain go out with payee positive pay and tighter mailing practices. Unclaimed checks are their own loose end, and handling stale checks covers what to do when a check never gets cashed at all.
What I can't tell you is how quickly your particular vendors will move. Some convert on the first call, while others hold out for years, and the AFP data suggests vendor demands are the main reason companies keep writing checks at all.
How Corpay reduces check exposure
The hardest part of cutting check-washing risk is converting vendors who've always been paid by check, one phone call at a time. Corpay takes that work off AP. Corpay payments automation is fully managed AP that enrolls suppliers and pays each one by virtual card, ACH, or check, so fewer payments go out on paper and the ones that do are handled within one program.
For card-accepting suppliers, Corpay virtual cards, including single-use virtual cards, replace mailed checks with card numbers that are useless after one payment, and Corpay customers earn $800M+ in rebates per year. Payments post to your ERP through 100+ integrations, including NetSuite, Sage Intacct, Business Central, and Acumatica, and most programs are live in weeks. The wider fraud picture is covered in the rise of check fraud and in payment fraud prevention.
Frequently Asked Questions
What does the term check washing mean?
Check washing means chemically removing the ink from a stolen check so the payee name and amount can be rewritten. The altered check is then deposited, often through mobile deposit, into an account the criminal controls.
Will using a Sharpie prevent check washing?
It helps on hand-written checks, since pigment ink resists common solvents better than ballpoint ink. It doesn't stop counterfeiting from a stolen check's account details, and it doesn't apply to printed business checks, which rely on security stock and positive pay.
How can banks detect check washing?
Banks detect altered checks mainly through positive pay, comparing presented checks to the issuer's file of checks written. Payee positive pay also compares the payee name, which is what catches a washed check where only the name was changed.
Who is liable for a washed check?
It depends on the deposit account agreement, how fast the business reported the altered item, and whether it used controls such as positive pay the bank offered. Businesses that skip available controls or report late often bear more of the loss.
Is check washing still common?
Yes. FinCEN reported check-fraud suspicious activity reports nearly doubling from 2021 to 2022, and organizations still rank checks as the payment method most targeted by fraud. As long as checks go through the mail, washing remains a live risk.
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