In addition to the regular postage rates, the 2014 extra postage fee for a square envelope is 20 cents for a 1oz envelope and 21 cents for a 2 oz envelope (additional fees may be charged for larger sizes). There is an additional charge because square envelopes cannot be run through the regular automated postal machines, thus requiring special handling.
Square envelopes are identified by the United States Post Office (USPS) as nonmachinable, meaning they cannot be sent through the typical postal reading machines and must be handled by human workers. As such, square envelopes require extra postage, called a nonmachinable surcharge. Nonmachinable items typically have one or more of the following characteristics:
- May jam postal equipment
- May be difficult to process
Regular envelopes are rectangular in shape and provide a long end for the machinery to grab for processing. As the envelope travels, machines locate the stamp and address, but such processing is made more difficult or impossible when the envelope is square or not a typical size. Such envelopes are better handled by people, which increases processing costs.