A First-Class Mail letter can require a nonmachinable surcharge when its shape, rigidity, closure, or thickness prevents normal machine processing. As of July 12, 2026, the surcharge is $0.49 in addition to the applicable letter postage. A one-ounce letter at $0.82 therefore totals $1.31 when it qualifies as a nonmachinable letter.
The surcharge does not make every object mailable as a letter. A piece that is too rigid, too thick, nonrectangular, or not uniformly thick may pay a parcel price instead. Check the live USPS Notice 123 and ask a clerk to inspect borderline mail.
Common nonmachinable characteristics
- A square envelope or another shape whose aspect ratio falls outside machinable standards.
- A piece that is too rigid to bend through letter-processing equipment.
- An uneven item caused by a pen, key, button, thick decoration, wax seal, or bulky enclosure.
- A closure, clasp, string, or button that interferes with processing.
- An address parallel to the shorter dimension rather than the long edge in a way covered by USPS standards.
Not every greeting card marked “extra postage required” has the same problem. Weight, dimensions, rigidity, and decorations must be evaluated on the finished, sealed envelope.
2026 examples
| Example | Likely question | What to do |
|---|---|---|
| Square wedding invitation under 1 oz | Aspect ratio / shape | Check letter dimensions and add the current surcharge if it remains a nonmachinable letter |
| Rectangular card with wax seal | Uneven thickness or rigidity | Take a complete sample to a Post Office before mailing the batch |
| Rigid photo mailer | May not qualify as a letter | Ask whether parcel pricing applies; a surcharge alone may be insufficient |
| Normal flexible 2 oz letter | Weight only | Pay the two-ounce letter rate; nonmachinable surcharge is not automatic |
How many Forever stamps?
At current values, two Forever stamps provide $1.64, which covers the $1.31 one-ounce nonmachinable letter amount but overpays by $0.33. Exact postage can be made with one Forever stamp plus $0.49 in additional denomination stamps. The correct combination changes when the piece weighs more than one ounce.
Use our calculator for common current amounts, but treat its result as stamp math after classification—not a substitute for a physical inspection.
Before mailing invitations or a large batch
- Assemble one envelope with every insert and decoration.
- Seal, weigh, and measure that exact sample.
- Check whether thickness is even and whether the piece bends.
- Bring it to a Post Office and ask which class and price apply.
- Mail a test piece early when timing matters.
Hand-cancel requests and nonmachinable pricing are not the same thing, and special handling cannot be guaranteed merely because extra stamps were added. Design invitations with mailing equipment in mind: use a rectangular envelope, avoid loose objects, keep decorations flat, and place bulky elements inside an inner envelope when appropriate.
Sources and limits
This page uses USPS Notice 123, the Domestic Mail Manual letter standards, and the July 2026 USPS price announcement. Rates were checked August 12, 2026. Local acceptance and the physical behavior of a mailpiece cannot be verified online; when a piece is close to a size or flexibility boundary, USPS inspection controls.