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POSTNET (POSTal Numeric Encoding Technique) was developed for use by the United States Postal Service (USPS) to automate the sorting of mail. The code comprises two frame bars at the beginning and end, combinations of five long and short bars for each of the ZIP code digits, and five more long and short bars for the check digit. Each digit from zero to nine is a unique pattern of long and short bars. The eleven-digit bar code is developed from the nine-digit ZIP code and the last two digits of the street address.

POSTNET is a demanding bar code symbology because it has a size and placement requirement. It cannot be reduced or enlarged. Bar width, height, and spacing are fixed.

Guidelines for creation and use of POSTNET are set by the USPS. You can obtain copies of the Domestic Mail Manual and/or Publication 25 from the USPS for an explanation of these guidelines.



FIM (Face Identification Marking) was developed as part of the POSTNET barcoding system. FIM is used by the cancelling machines to sort mail according to whether or not they have bar codes and their postage requirements. There are three types of FIM called FIM A, FIM C, and FIM D.

The FIM types have the following meanings:

FIM A - Postage required, POSTNET bar code included

FIM C - Postage prepaid, POSTNET bar code included

FIM D - Postage required, POSTNET bar code not included

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