What is the Non-Machinable Surcharge for First-Class Mail®?
A nonmachinable mailpiece is a mailpiece that must be sorted outside of the standard, automated mail process. Because it is more expensive to processes these mailpieces, a surcharge applies to them.
  - For pieces more than 4-1/4 inches high or 6 inches long, the thickness is less than 0.009 inch
 
  - The length divided by height is less than 1.3 or more than 2.5 (length is the dimension parallel to the address)
 
  - It is poly-bagged, poly-wrapped, enclosed in any plastic material, or has an exterior surface made of a material that is not paper
 
  - It has clasps, strings, buttons, or similar closure devices
 
  - It is too rigid or contains items such as pens, keys or coins that cause the thickness of the mailpiece to be uneven
 
  - It has a delivery address parallel to the shorter dimension of the mailpiece
 
Also, the nonmachinable rate may not be charged for round-trip mailings of letters containing discs (discs mailed under specific criteria from a mailer who expects to receive the disc back from a subscriber) that are placed into the mailstream either presorted or returned single-piece.
Use the Postal Price Calculator to help determine if your letter or flat is nonmachinable and what the surcharge is.