The safest way to mail a check is to write it with wash-resistant ink, conceal it inside a security-tinted envelope, and drop it off inside your local post office rather than in an outdoor mailbox. Each of those steps targets a specific type of mail theft or fraud, and together they make your check far harder to steal or alter in transit.
Write the Check With the Right Pen
Check washing is a common fraud technique where a thief steals a check from the mail, uses chemicals to dissolve the ink, and rewrites the payee name and dollar amount. A standard ballpoint pen offers almost no resistance to this process.
Gel-based pens with permanent, wash-resistant ink are your best defense. The Uni-ball 207 is widely recommended because its “Super Ink” formula soaks into paper fibers rather than sitting on top of them, making it extremely difficult to wash away. You don’t need that exact brand, but look for any gel pen marketed as security ink or check-safe ink. Avoid felt-tip markers and standard ballpoints.
Beyond the pen itself, fill in every field on the check completely. Draw a line through any blank space after the payee name and after the written dollar amount so no one can add extra characters. If you’re mailing a check for $500, write “Five hundred and 00/100” followed by a line filling the rest of the space.
Use a Security-Tinted Envelope
A plain white envelope lets someone hold it up to a light and read what’s inside. Security-tinted envelopes have a printed pattern on the interior, typically a crosshatch or geometric design, that blocks visibility from the outside. They’re sold at any office supply store and cost only slightly more than standard envelopes. Look for envelopes made from at least 24-lb paper, which adds durability and makes the contents even harder to see through.
Don’t write “check enclosed” or anything similar on the outside. The envelope should look like any other piece of ordinary mail. If the check fits inside a folded sheet of paper (a brief letter or even a blank piece of printer paper), wrap it that way for an extra layer of concealment.
Choose a Secure Drop-Off Location
Where you deposit the envelope matters as much as how you prepare it. Outdoor blue USPS collection boxes have become frequent targets for mail theft, with criminals using tools or even stolen master keys to access them. USPS itself recommends depositing outgoing mail inside your local post office, at your place of business, or by handing it directly to your letter carrier.
If you must use an outdoor collection box, do it right before the last scheduled pickup of the day (the time is printed on the box). Mail sitting overnight in an unattended box is at the highest risk. Dropping it off just before pickup minimizes the window of exposure.
Add Tracking or Proof of Delivery
For checks worth more than a trivial amount, paying a few extra dollars for tracking gives you a paper trail and, in some cases, physical security upgrades.
- Certified Mail ($5.30): This gives you proof that you sent the item and lets you track delivery. When combined with a return receipt, you also get the recipient’s signature as confirmation. The recipient may need to show ID before the postal worker hands it over. This is a good option for rent checks, tax payments, or any situation where you need to prove the check was received.
- Registered Mail (starting at $19.70): This is the most secure option USPS offers. Every registered item is logged at each step of its journey and kept under lock or in a secure area, separate from regular mail. You can insure the contents for up to $50,000. It’s slower than standard delivery because of the chain-of-custody process, but it’s the right choice for high-value checks.
Both services require you to bring the envelope to a postal employee at the counter. You can’t use a collection box or leave it in your mailbox for pickup.
Limit the Information on the Check
Your check already contains your name, address, bank routing number, and account number. Don’t add anything that makes identity theft easier. Avoid printing your Social Security number, driver’s license number, or date of birth on checks. If a payee requires a reference number (like an account number for a utility bill), write it in the memo line only.
Some people prefer to use checks that don’t include a home address, listing only a name and city/state instead. If your bank allows it, this reduces the personal information a thief could harvest from a stolen check.
Consider Whether a Check Is Necessary
Sometimes the safest way to mail a check is to not mail one at all. Electronic payments, bill pay through your bank, wire transfers, and services like Zelle eliminate mail theft risk entirely. Many landlords, government agencies, and businesses that once required paper checks now accept electronic alternatives.
When a paper check is genuinely the only option, the steps above, using wash-proof ink, a security envelope, an indoor drop-off point, and tracking for anything significant, cover the realistic threats your check faces between your hands and the recipient’s mailbox.