Can you add postage to a prepaid label?
With stamps, yes: stamps already on a piece count toward the postage at face value, so you add only the difference. A second printed postage label is different: USPS says it must equal the total postage required, not just the shortfall.
So for an online label bought at the wrong weight, the cheaper fix is a refund of the unused label and a new one: a 2 lb Ground Advantage label ($10.50 to Zone 5) on a package that weighs 2 lb 6 oz needs the 3 lb price, $12.12. A second label would cost the full $12.12 on top of the first; reprinting costs $1.62 more once the first label is refunded.
Rates verified on
Postage in the examples is from Notice 123 effective Oct 4, 2026, which includes USPS's temporary holiday prices for Ground Advantage and Priority Mail until 12 a.m. CT Jan 17, 2027. The fees quoted here are the same as in the July 12, 2026 edition, before the holiday prices began.
Free printable USPS cheat sheet: package prices, extra-service fees and stamps
The rule, in USPS's words
“Postage stamps or meter stamps originally affixed to insufficiently prepaid mail are accepted in payment of postage to the amount of their face value when the mail is again presented for mailing.”
“Indicia for additional postage on shortpaid mailpieces must equal the total amount of required postage.”
“For mailpieces with a detected postage discrepancy when postage is due, corrective measures may include one of the following”
“Delivering the mailpiece to the addressee and collecting the deficiency as postage due.”
“the customer will be notified by the PES provider to provide funds to resolve the discrepancy within 14 calendar days, or 10 business days if by electronic means”
“The sender may affix the additional postage, cross out the reason for nondelivery, and remail the piece.”
What each fix costs, with examples
| Fix | You pay | Why |
|---|---|---|
| Refund the unused 2 lb label and print a 3 lb one | $12.12, with the $10.50 label refunded: $1.62 more | Only one label, at the right weight |
| Add a second printed label for the difference | Not allowed: a second label must be the full $12.12, so $22.62 in all | Additional-postage indicia must equal the total postage (DMM 604.4.5.1) |
| Mail it short | The postage due, collected one of four ways | Charged through your label provider, returned to you, collected from the buyer at delivery, or collected at the counter (DMM 604.4.4.3) |
| Stamped parcel, retail price: $14.85 in stamps, weighs 2 lb 6 oz | $0.85 more in stamps ($15.70 in all) | Stamps already on it count at face value (DMM 604.8.1.4) |
Edge cases
- Returned for postage: a stamped First-Class Mail piece that comes back marked “Returned for Additional Postage” can go out again: add the missing stamps, cross out the reason and remail it (DMM 604.8.1.2).
- Already mailed short on a printed label: USPS can charge the shortfall through your label provider, return the package, deliver it and collect postage due from the buyer, or collect it at the counter (DMM 604.4.4.3). If the provider can't take the full amount, you get 14 calendar days (10 business days if notified electronically) to pay before printing can be suspended (DMM 604.4.4.4).
- Stamps on top of a printed label: DMM 604.8.1.4 credits “postage stamps or meter stamps” already on the piece; it doesn't say a PC Postage label counts as a meter stamp, so don't count on stamps topping up a label you printed online.
- A label someone else bought (a buyer's or a store's prepaid return label): a second printed label would have to pay the full price (DMM 604.4.5.1), so ask whoever bought it for a label at the right weight.
- Weight rounds up: any fraction of a pound bills as the next pound, so 2 lb 1 oz is already short on a 2 lb label (weight rounding).
What to do
- Weigh the packed box before you print; if a printed label turns out short and is unused, request a refund (see refunds for unused labels) and print one at the right weight.
- With stamps, add only the difference: the stamps already on the piece count at face value.
- Don't send a known-short package: postage due collected from the buyer at delivery is a bad first impression, and a returned package costs you the trip.
Questions
Can I put stamps on a package that already has a shipping label?
The DMM credits stamps or meter stamps already on a piece at face value (DMM 604.8.1.4), and says a second printed postage indicium must cover the whole price (DMM 604.4.5.1). It doesn't say stamps can top up a label you printed online, so the safe fix for a short label is a refund and a correct label.
What happens if I mail a package with not enough postage on a label?
USPS may charge the difference through your label provider, return the package, deliver it and collect postage due from the recipient, or collect it at the counter (DMM 604.4.4.3).
Can I add postage to a prepaid return label?
Not by printing a top-up: an additional-postage label must equal the total postage required (DMM 604.4.5.1). Ask whoever issued the return label for one that matches the package's weight.
Sources
Rates verified on from each official page below.
- USPS Notice 123, Price List (effective Oct 4, 2026)
- USPS Domestic Mail Manual 604: postage payment, rounding and postage discrepancies
Free 1-page Reseller Cheat Sheet: fees on 8 platforms, Media Mail and stamp prices
What each platform takes from a $10, $25 and $50 sale, Media Mail 1-10 lb, Ground Advantage to Zones 1, 5 and 8, and the Forever stamp, on one printable page. The link appears as soon as you sign up.