What makes a letter nonmachinable, and what does USPS charge?
A letter-size piece pays a 49¢ nonmachinable surcharge on top of postage if it is square or long and narrow, rigid, lumpy, in plastic, closed with a clasp or string, or addressed along the short side, so a 1 oz square card costs $1.31 with stamps.
Postcards never pay it, and a large envelope that fails the same kind of tests doesn't pay a surcharge: it becomes a parcel instead (DMM 101.6.3).
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.
The rule, in USPS's words
“Letters that meet one or more of the nonmachinable characteristics in DMM 101.1.2 are subject to the $0.49 nonmachinable surcharge.”
“Has an aspect ratio (length divided by height) of less than 1.3 or more than 2.5.”
“Is too rigid (does not bend easily when subjected to a transport belt tension of 40 pounds around an 11-inch diameter turn).”
“Contains items such as pens, pencils, keys, or coins that cause the thickness of the mailpiece to be uneven”
“Has a delivery address parallel to the shorter dimension of the mailpiece.”
“Pieces mailed at the card price are not subject to the nonmachinable surcharge.”
What it costs, with examples
| Envelope | Why | Postage |
|---|---|---|
| #10 business envelope (9-1/2 x 4-1/8 in.), 2 oz | aspect ratio 2.3: machinable | $1.11 |
| 6 x 6 in. square card, 1 oz | aspect ratio 1.0, under 1.3 | $0.82 + 49¢ = $1.31 |
| 5 x 8 in. card addressed along the 5 in. side, 1 oz | length 5, height 8: ratio 0.625 (USPS's example, DMM 601.1.1.3) | $1.31 |
| #10 envelope with a key inside, 1 oz | uneven thickness | $1.31 |
| Letter in a clear plastic sleeve, 1 oz | enclosed in plastic | $1.31 |
| 4 x 6 in. postcard | card price, never surcharged | 65¢ |
Edge cases
- Thin and big: a letter over 6 in. long or 4-1/4 in. high that is less than 0.009 in. thick is nonmachinable (DMM 101.1.1, 1.2).
- Address direction counts: length is the side parallel to the address, so the same 5 x 8 in. card is machinable addressed one way and nonmachinable the other (DMM 601.1.1.3).
- Paper windows are fine: windows in paper envelopes don't make a letter nonmachinable (DMM 101.1.2).
- Large envelopes: the aspect ratio test is for letters. A flat is judged on size, flexibility and even thickness, and one that fails pays parcel prices (flat or parcel).
- Loose odd-shaped items such as pens, key rings or bottle caps aren't allowed in paper letter or flat envelopes unless wrapped within the other contents (DMM 601.3.3).
- A stamp for it: USPS sells a Forever stamp worth the nonmachinable surcharge price (DMM 604.1.1; stamp prices).
- Short-paid: a nonmachinable First-Class Mail letter without enough postage is returned to the sender for more postage, not delivered postage-due (DMM 604.8.1.3).
What to do
- Use a rectangular envelope with an aspect ratio between 1.3 and 2.5 and address it along the long side.
- Keep contents flat; wrap any hard item inside the other contents, or ship it as a parcel.
- For a card in a rigid holder that needs tracking, a Ground Advantage label online costs $7.33 to $8.95 by zone (how to ship trading cards).
Questions
Do square envelopes cost extra?
Yes. A square letter's aspect ratio is under 1.3, so it pays the 49¢ nonmachinable surcharge: $1.31 for 1 oz with stamps (DMM 101.1.2; Notice 123).
Does a postcard pay the nonmachinable surcharge?
No. Pieces mailed at the card price are not subject to it (DMM 133.1.7).
Sources
Rates verified on from each official page below.
- USPS Notice 123, Price List (effective Oct 4, 2026)
- USPS Domestic Mail Manual 101: physical standards for retail letters, flats and parcels
- USPS Domestic Mail Manual 133: First-Class Mail and Ground Advantage retail prices and eligibility
- USPS Domestic Mail Manual 601: mailability, packaging and USPS-produced packaging
- 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.