Postnet

POSTNET (Postal Numeric Encoding Technique) is the US Postal Service barcode for ZIP code information, qualifying mailers for postage discounts.

The POSTNET (Postal Numeric Encoding Technique) barcode was invented by the US Postal Office to encode ZIP information. Making your letter printing system POSTNET-capable enables you to receive a discount on postage.

US delivery address coding can take one of three forms:

• 5-digit ZIP
• 5-digit ZIP + 4 code
• 11-digit delivery point code

So a valid POSTNET barcode contains either 32, 52, or 62 bars (including frame bars and check digit, see below).

POSTNET is a numeric symbology. Unlike most other symbologies, POSTNET has requirements on the actual bar height and width. The information is encoded in the height and has nothing to do with the spacing.

The check digit is based on the Mod 10 algorithm. The value of the check digit is such that, when added to the sum of the other digits in the barcode, it results in a total that is a multiple of 10.

For example, in the diagram above, the check digit for 91801 is 1, since 9+1+8+0+1+1=20, which is two times 10.

The POSTNET barcode starts with a long bar (frame bar) and ends with a frame bar. Between these two frame bars is the encoded address information, followed by a check digit. Each code character is made up of five bars, either long or short. If we use 1 to represent the long bar and 0 to represent the short bar, each character is encoded based on the table to the left.

The POSTNET barcode should be placed in the lower right corner of the envelope or in the address block, as illustrated below. For more information, visit the US Postal Office website.