LetterAgent
Mail physical letters by just asking your AI assistant.
Home > Guides > Protecting a mailed check
Write the check with a pigment-based gel pen, whose ink bonds to the paper fibers, and fill every line with no blank spaces for a thief to exploit. Never leave it in your home mailbox with the flag up: hand it to a clerk or drop it in a collection box close to pickup time. If a check goes missing, tell your bank immediately.
| Protection | Why it works |
|---|---|
| Pigment-based gel ink pen | The ink bonds into the paper fibers; household chemicals that lift ballpoint ink leave gel ink readable |
| Fill every line, start at the far left | Blank space is where altered payees and amounts get written in |
| Draw a line through unused space on the amount line | Closes the gap a thief would use to add digits |
| Hand the envelope to a clerk or use a collection box near pickup time | Minimizes the window when the envelope sits unattended and fishable |
| Locking mailbox for anything left at home | A raised red flag advertises outgoing mail to everyone passing by |
Thieves steal envelopes containing checks, then use common chemicals (acetone and similar solvents) to dissolve the ink while leaving the paper intact. The payee line and the amount get rewritten, usually to a much larger figure, and the altered check is cashed or deposited. The Postal Inspection Service flags this as a recurring mail crime, and the victims are often ordinary people who mailed rent or contractor payments. The uncomfortable truth: ordinary ballpoint ink washes off easily, which is why the pen you choose is the single most effective defense.
Use a black pigment-based gel pen. Ballpoint ink sits on the surface of the paper and lifts with solvents; pigment gel ink soaks into and bonds with the paper fibers, so washing leaves the writing legible or destroys the paper trying. This is not marketing: banks and fraud investigators recommend gel ink for this exact reason. Keep one such pen where you write checks and do not substitute whatever pen is nearest. Blue ink is traditional, but black gel gives scanners and the human eye the best contrast if the check is ever examined for alterations.
Deny the thief working room. Write the payee name starting at the far left of the line with no leading gap. Spell out the amount and draw a line from the end of the words to the edge of the amount area so nothing can be added after it. Fill the numeric amount box tightly, close to the printed dollar sign. Never leave the memo line blank on a check going to someone you do not know well: it matters less than the payee and amount, but a filled memo removes one more ambiguity. And sign every check the same way you always do: your bank compares signatures, and a consistent signature is your silent witness.
The weakest link is usually not the check but the mailbox. A home mailbox with the red flag up is an announcement that outgoing mail is waiting; thieves cruise neighborhoods for exactly that signal. The blue USPS collection boxes are better but not immune: thieves fish envelopes out of them too, so drop your check as close to the posted pickup time as possible rather than the night before. Best of all is handing it directly to a clerk inside the post office. For recurring payments, consider whether the check needs to be mailed at all: most banks offer free bill pay that sends a check or electronic payment without you touching an envelope.
Act the same day you notice. Call your bank and ask for a stop payment on the check number; there is usually a small fee and a time limit, so do not wait. Check your account for unfamiliar withdrawals and look at the bank's image of any check that did clear: washed checks often show subtle smudging around the payee or amount. File a report with the Postal Inspection Service, and if identity details were in the envelope, consider the usual identity-theft precautions. Businesses writing many checks should ask their bank about Positive Pay, a service where the bank matches each presented check against a list you provide and flags anything that does not match.
Ready to mail it? Send your letter with LetterAgent: describe it to your AI assistant, approve the exact quoted price, and it is printed and mailed.
LetterAgent is a working name. Prices include print, postage, and our service fee. US prices in USD, Canadian prices in CAD (Canadian prices exclude applicable sales tax, added at checkout). Currently in private testing.
Need help? Ask your assistant: it can check a job's status any time. If it ever can't handle something: hello@getletteragent.com