Reusing a postage stamp is a federal crime, even when the stamp looks clean and shows no cancellation mark. Under 18 U.S.C. § 1720, placing a previously used stamp on a new piece of mail can bring a fine of up to $100,000, up to a year in prison, or both. The rule applies whether the first letter was delivered, returned to sender, or never left your mailbox.
Stamps that have never traveled through the postal system are a different matter. Those remain valid indefinitely and can be used whenever you like.
When a Stamp Counts as Used
A stamp becomes “used” the moment it pays for a piece of mail that enters the postal system, not when a cancellation mark lands on it. The U.S. Postal Service is explicit on this: a stamp that has already been used to send mail cannot be placed on another mailpiece, even if the Postal Service never canceled or defaced it.
Cancellation marks are there to make reuse obvious, not to define it. Sorting machines apply black ink, wavy lines, or circular date postmarks, and some machines also spray fluorescent or invisible inks that the naked eye cannot detect but that postal equipment reads on a second pass. A clean-looking stamp on a delivered envelope does not mean the system missed it.
Returned Mail and Uncanceled Stamps
This is the scenario that trips most people up. You mail a letter, it comes back marked “Return to Sender” because of a bad address, and the stamp looks untouched. Common sense says the stamp is still good. Federal law says otherwise.
Once a stamp enters the mailstream, it has paid for postal handling regardless of whether the letter reached its destination. The USPS makes no exception for returned mail. Even without a visible cancellation, the stamp cannot legally be placed on a new envelope, and the prohibition in 18 U.S.C. § 1720 still applies.
The practical risk is real too. Automated equipment may have already applied invisible fluorescent markings on the first trip. If those are detected on a second pass, the new letter will be returned to you for proper postage or delivered with a postage-due notice that the recipient has to pay.
What 18 U.S.C. § 1720 Prohibits
The statute reaches three separate acts:
- Placing any previously canceled stamp on mail, or attempting to.
- Washing, scraping, or chemically treating a stamp to remove postal markings, or helping someone else do so.
- Knowingly placing any stamp already used for postage onto a new mailpiece, canceled or not.
For an ordinary sender, the maximum penalty is a fine of up to $100,000, imprisonment for up to one year, or both. The U.S. Postal Inspection Service investigates these cases. Large-scale counterfeit or washed-stamp operations draw the most attention, but the statute applies just as much to peeling a stamp off one envelope and sticking it on another. Post offices nationwide post the warning in plain terms: reusing a stamp “whether cancelled or not” is a federal crime.
What Happens If You Try It
Mail sent with invalid postage, including a reused stamp, is endorsed “Returned for Postage” and sent back to the return address with no delivery attempt. If there is no return address, or the return address matches the delivery address, the piece is treated as dead mail.
A single reused stamp on a personal letter is unlikely to trigger a federal case on its own. The legal exposure still exists, and patterns of reuse or any attempt to sell washed stamps can and do lead to prosecution.
Stamps You Can Still Use
Stamps that have never been affixed to a mailed item remain fully valid, no matter how old. A sheet purchased years ago works fine today, though you may owe makeup postage if rates have gone up.
Forever stamps are the easiest case. Each one always covers the current First-Class Mail one-ounce letter rate, which is $0.78 as of January 2026. A Forever stamp bought in 2007 at 41 cents still covers the full 78-cent rate today with nothing added.
Denomination stamps that show a specific cent value also stay valid indefinitely. Old 55-cent stamps work if you add 23 cents to reach the current rate, and the USPS sells 1-cent and 3-cent stamps for exactly this kind of gap.
Exchanging Stamps at the Post Office
If you have unused stamps you no longer need, or that got damaged before you could mail anything, exchanging them is usually simpler than improvising.
Stamps you bought by mistake can be exchanged at full postage value if they are in full, unopened panes, sealed coils, or full boxes of stamped envelopes. Stamps that became unusable from humidity, moisture, or similar causes can be swapped for equal stamps up to $100 per transaction, provided they were on sale within the past 12 months and are still in substantially whole condition. Stamps that were defective when sold can be exchanged at full value with no such limits.
Cut-outs from stamped envelopes, pieces of postal cards, and stamps mutilated beyond recognition are not exchangeable. For leftover denomination stamps you simply want to spend, the easiest path is pairing them with low-value makeup stamps until the total reaches the current rate.