Mail Theft, Check Washing and Mailed Payments

Why this matters

A shop is exposed to check fraud from two directions at once. Its own checks to subcontractors and suppliers travel through the mail and can be stolen and rewritten. And its customers' checks travel through the mail toward it, and when one of those is stolen, the customer swears they paid, the invoice says they did not, and the shop is caught in the middle of a crime it had nothing to do with. Mail theft aimed at checks rose sharply enough in the early 2020s that the Treasury's Financial Crimes Enforcement Network issued a nationwide alert on it in 2023. The fixes are different for each direction, and confusing them is the most common mistake.

How a mailed check gets turned into money

Thieves take checks from three places: blue street collection boxes (often opened with stolen or copied postal keys), home and office mailboxes with the flag up, and occasionally from inside the mail stream. Then one of two things happens.

Washing. The thief uses a household solvent to lift the ink from the payee line and the amount, leaving the signature, which is usually in a different ink or is simply not touched. They write in a new payee, often their own name or a shell account, and frequently a larger amount. The check is real paper, drawn on a real account, carrying a real signature. That is why it clears.

Copying. The thief scans the check and prints counterfeits. Every check carries the bank's routing number and the account number along the bottom, in the magnetic-ink line the bank's machines read, so one stolen check is a template for many forgeries on the same account.

The anatomy shows what a thief changes and what a bank checks:

+---------------------------------------------+
| SHOP NAME                       No. 4127    |
| PAY TO   [payee line]   <- washed, rewritten|
| AMOUNT   [figures]      <- washed, raised   |
|          [words]        <- washed, rewritten|
| MEMO     [invoice no.]  <- usually left     |
|                  [signature]  <- kept       |
| routing  account  4127  <- copied for fakes |
+---------------------------------------------+
 positive pay compares:    number, amount
 payee positive pay adds:  payee name

The bottom two lines are the point. Ordinary positive pay compares the check number and the amount to the list you sent the bank. A washed check whose thief kept the original amount sails straight through it, because the number and the amount still match. Only payee positive pay, which also compares the name, catches the commonest kind of wash.

Your outgoing checks: what each control catches

Payee positive pay is the strongest single control for checks you write. It catches a changed payee, a raised amount, and a counterfeit using a check number you never issued. Setting it up belongs to a sibling. See related: Setting Up Bank Alerts and Dual Approval for Outgoing Money.

Ink matters at the margin. Pigmented gel ink soaks into the paper fibers and resists solvents far better than ordinary ballpoint, which sits on the surface. It makes washing harder, not impossible, and it does nothing against copying.

Where you post it matters more. Hand outgoing checks to a clerk at the post office counter, or drop them inside the post office, rather than in a street box or the office mailbox with the flag up. Street boxes are emptied on a schedule, and anything left overnight or over a weekend sits in the box thieves target.

Positive pay changes who bears the loss, not just whether it happens. Many business account agreements now state that if the bank offered positive pay and you declined it, check fraud it would have caught is your loss. Read the check fraud section of your own agreement. Beyond the agreement, who bears an altered-check loss among you, your bank and the bank that took the deposit is governed by UCC Articles 3 and 4 as your state has enacted them, and the answer turns on facts like how quickly you reviewed your statement. That is a question for your banker and, if the amount is real, your attorney. This is not legal advice.

The trade-off when you stop mailing checks. Paying subcontractors and suppliers electronically removes the mail risk, and it opens a different one: fraudsters impersonate a supplier and ask you to change the bank details you pay. Moving outgoing payments to ACH is right for most shops, but only alongside a firm rule for bank detail changes. See related: The Vendor Bank Detail Change SOP.

Your customers' checks: the risk positive pay does not touch

None of your bank's check controls help when a customer's check to you is stolen, because that check is drawn on the customer's account, not yours. Their bank pays it to the thief, and the first anyone hears of it is your overdue reminder.

What that call looks like. The customer says they mailed a check two weeks ago. Your records show nothing received. The worst response is to treat them as a liar; the second worst is to write the invoice off on their word. The useful response is to ask them to check their own bank's record of the check: whether it has cleared, and if so, to whom. A washed check that cleared shows a payee name that is not yours, and the customer's bank can provide an image. That is a fraud claim for the customer to make with their bank, quickly, because banks set short deadlines for reporting a problem on a statement. The customer should also report the stolen mail to the U.S. Postal Inspection Service, which tracks these thefts by route and collection box.

What the shop can reasonably do. Hold off on late fees and collection steps while the customer pursues it, note the account, and ask them to pay by another route in the meantime if they can. Whether the shop can insist on payment before the customer's bank resolves its claim is a business decision; legally, the invoice is still unpaid, but the customer relationship is usually worth more than a few weeks of patience.

Where your incoming payments go. Have customer checks mailed to a post office box or a bank lockbox rather than the office mailbox, which on a busy day nobody empties until evening. A lockbox (where the bank receives and deposits your mailed payments directly) also takes checks out of the office entirely.

Moving customers off mailed checks without losing them

The durable fix for incoming checks is fewer of them. The friction comes from asking customers to change a habit, so make the electronic route easier than the envelope.

Put a pay link on every invoice. An invoice that arrives by email or text with a link the customer can tap to pay by card or bank transfer converts a large share of check writers without a single conversation. Bank transfer (ACH) through your processor usually costs the shop a much smaller percentage than a card.

Take payment at the job. A tech who asks for payment on completion, on a tablet or card reader, never generates a check at all.

Offer auto-pay at the moment it is easiest to say yes. For recurring service, the renewal or the first visit of the season is when a customer is already deciding; that is when to offer a card or bank account on file.

Do not punish checks into extinction. Some customers, often older ones, will keep paying by check whatever you do. For them, a pre-addressed reply envelope to your post office box, with a small printed note asking them to drop it inside a post office rather than in a home mailbox, protects them without pushing. If you consider a card surcharge to steer payment, note that card surcharge rules vary by state as of 2026, and a few states, Massachusetts and Connecticut among them, prohibit surcharges outright, alongside the card networks' own rules. Check your state's current rule before adding one.

Worked example: a lawn care shop with a check-heavy book

The starting point. A lawn and landscape shop with 180 recurring residential customers billed monthly through the season. About 40 percent of them, 72 customers, paid by mailed check, sent to the office mailbox. That is 72 checks a month. In the prior season the shop had three customers report a mailed check that never arrived; two of them later found the check had cleared to a stranger's name.

What it did. At the spring renewal, every customer received the renewal by email with a pay link and an offer to put a card or bank account on file for monthly auto-pay. Techs were told to mention it on the first cut. Check payers who did not switch got reply envelopes addressed to a new post office box, with the drop-it-inside note.

The result after one season. Check payers fell from 72 customers to 27, from 40 percent of the book to 15 percent. Monthly checks fell by the same 45, from 72 to 27, a drop of 62.5 percent. Of the 45 who switched, most went to bank transfer on file, which cost the shop a smaller percentage per payment than card. Missing-check reports that season: none, though with 27 checks a month still in the mail and only three incidents the year before, one quiet season is not proof the risk has gone. It is fewer envelopes exposed, which is the only thing the shop controls.

What would have changed the approach. A commercial book, such as property managers paying from accounts-payable departments, behaves differently: those customers often pay by check because their own process requires it, and the better move is to ask them to pay by ACH to your account, with your bank details confirmed through their vendor-setup process rather than sent in an email. And a shop whose customers skew heavily elderly might accept a slower switch, putting the effort into the reply envelope and the post office box rather than into the pay link.

How to know the exposure is shrinking

Count two things monthly: the number of checks you receive, and the number you write. Both should trend down. Then once a quarter, compare the shop's own check register to the bank's cleared items and confirm every cleared payee name matches what was written. If the bank offers payee positive pay, it does this for you on every check; if you have not taken it, that quarterly comparison is the manual version, and it is the moment you learn whether anything has been washed.

References

• FinCEN Alert FIN-2023-Alert003, on the nationwide surge in mail theft-related check fraud (February 2023)
• U.S. Postal Inspection Service, for reporting stolen mail and mail theft
• UCC Articles 3 and 4 (negotiable instruments; bank deposits and collections), as enacted by your state
• See related: Setting Up Bank Alerts and Dual Approval for Outgoing Money
• See related: The Vendor Bank Detail Change SOP