What Is a Nonmachinable Surcharge?
A letter can be within the basic size limits and still require a nonmachinable surcharge because of its shape, rigidity, closure, address direction, or uneven thickness.
First Confirm That the Piece Is a Letter
Under current retail standards, letter-size mail is at least 5 inches long, 3.5 inches high, and 0.007 inch thick. It is no more than 11.5 inches long, 6.125 inches high, or 0.25 inch thick, and no more than 3.5 ounces. A piece outside the letter limits may be a flat or parcel rather than a letter with an added surcharge.
Current Nonmachinable Criteria
| Check | Criterion to apply to the completed letter |
|---|---|
| Aspect ratio | Length divided by height is less than 1.3 or more than 2.5. |
| Exterior material | Polybagged, polywrapped, enclosed in plastic, or an exterior surface that is not paper, subject to stated exceptions. |
| Closure | Clasps, strings, buttons, or similar closure devices. |
| Contents | Items such as pens, keys, or coins that create uneven thickness, or loose objects that are not secured. |
| Rigidity | The letter does not bend easily under the DMM transport-belt standard. |
| Thin oversized letter | More than 6 inches long or 4.25 inches high but less than 0.009 inch thick. |
| Address orientation | The delivery address is parallel to the shorter dimension. |
Self-mailers and booklets also have preparation standards. When the classification is uncertain, have the completed sample evaluated before preparing the full batch.
Two Concrete Examples
Six-inch square envelope: its aspect ratio is 6 divided by 6, or 1.0. Because 1.0 is below the 1.3 minimum, a letter-size square envelope is nonmachinable even if its weight, thickness, and contents otherwise qualify. Calculate its weight-based letter postage first, then add the current surcharge.
Five-by-seven-inch invitation: its aspect ratio is 7 divided by 5, or 1.4, so it passes the aspect-ratio test. That does not finish the review. A rigid insert, clasp, uneven decoration, excessive thickness, or address printed parallel to the five-inch side could still make it nonmachinable.
Price Examples at July 2026 Rates
| Qualifying domestic letter | Weight-based amount | With $0.49 surcharge |
|---|---|---|
| Up to 1 oz | $0.82 | $1.31 |
| Over 1 oz through 2 oz | $1.11 | $1.60 |
| Over 2 oz through 3 oz | $1.40 | $1.89 |
| Over 3 oz through 3.5 oz | $1.69 | $2.18 |
Frequently Asked Questions
Does one square envelope need the surcharge?
Yes, when it is mailed as a letter. A square has an aspect ratio of 1.0, below the machinable range of 1.3 through 2.5.
Does every wax seal trigger the surcharge?
No universal answer applies. Check whether the completed piece becomes rigid, uneven, too thick, or otherwise meets a listed criterion.
Is the surcharge the only extra amount for a heavy letter?
No. Determine the weight-based letter amount first, then add the surcharge when a nonmachinable characteristic applies.
What if the piece exceeds letter dimensions?
Use the correct flat or parcel classification rather than adding the letter surcharge to an ineligible piece.
After applying the dimensional and flexibility rules to the completed envelope, compare current postage stamp options for the calculated amount.
Sources and Scope
- USPS Domestic Mail Manual 101 sections 1.1, 1.2, and 6.3 for retail letter dimensions and nonmachinable criteria.
- USPS Notice 123 for prices effective July 12, 2026.
- USPS Postage Price Calculator for checking a specific mailpiece.
The examples assume the pieces remain eligible domestic letters. Final classification depends on the completed mailpiece.