The PostNet (Postal Numeric Encoding Technique) is a code by the US Post Office. It encodes the zip of the addressee in a machine readable format. This improves the speed of sorting and delivering the mail.
The PostNet barcode is constructed as follows:
- Start character
- Check digit
- Stop character
The check digit is calculated as follows: First add all digits. The difference of this sum to the next multiple of 10 is the check digit.
The PostNet barcode is used mainly in 3 variants, that differ in the length of the data:
- 5 digits POSTNET barcode: 5 digit long zip code
- ZIP + 4 POSTNET barcodes: 9 digit long zip code
- DPBC POSTNET barcode (Delivery Point barcode): 9 digit long zip code + 2 DPBC digits
The check digit of the PostNet barcode is not displayed in the plain text line.