Editing ZIP Code (section)

===Postal barcode===
{{main|Intelligent Mail barcode}}
The ZIP Code is often translated into an Intelligent Mail barcode printed on the mailpiece to make it easier for automated machines to sort. A barcode can be printed by the sender (some word-processing programs such as [[WordPerfect]]<ref>{{cite web |url=http://kb.iu.edu/data/aapk.html |title=Archived: How can I print routing barcodes on envelopes? – Knowledge Base |publisher=The Trustees of Indiana University |access-date=July 10, 2009 |archive-date=March 10, 2012 |archive-url=https://web.archive.org/web/20120310180946/http://kb.iu.edu/data/aapk.html |url-status=live }}</ref> include the feature), but this is not recommended, as the address-to-ZIP lookup tables can be significantly out of date.

Customers who send bulk mail can get a [[Discounts and allowances|discount]] on postage if they have printed the barcode and have presorted the mail. This requires more than just a simple [[typeface|font]]; [[mailing list]]s must be standardized with up-to-date [[Coding Accuracy Support System]] (CASS)-certified software that adds and verifies a full, correct ZIP+4 Code and an additional two [[Numerical digit|digit]]s representing the exact [[delivery point]].{{citation needed|date=April 2010}} Furthermore, mail must be sorted in a specific manner to an 11-digit code with at least 150 mailpieces for each qualifying ZIP Code. It must be accompanied by documentation confirming this. These steps are usually done with PAVE-certified software that prints the barcoded address labels and the barcoded sack or tray tags.{{citation needed|date = November 2018}}

The assignment of delivery point digits (the 10th and 11th digits) ensures that every mailable point in the country has an 11-digit number. The delivery-point digits are calculated based on the primary or secondary number of the address. The USPS publishes the rules for calculating the delivery point in a document called the CASS Technical Guide.<ref>{{cite web |url=http://www.ribbs.usps.gov/files/CASS/TECHNICAL_GUIDES/CASSTECH.PDF#page=40 |format=PDF |title=CASS Technical Guide |publisher=United States Postal Service |page=40 |access-date=July 10, 2009 |url-status=dead |archive-url=https://web.archive.org/web/20090419090333/http://ribbs.usps.gov/files/CASS/TECHNICAL_GUIDES/CASSTECH.PDF#page=40 |archive-date=April 19, 2009 }}</ref>