Data Files
03/08/2008
USPS-LR-L-62

This library reference documents the development of test-year volume, characteristics, and costs of processing Undeliverable-As-Addressed mail (UAA) mail. This is a Category 2 library reference sponsored by witness Cutting (USPS-T-26).

Tech Guides
05/01/2006
Z4 Info File Layout

This data file presents a table of codes for primary and secondary numbers to describe Z4Info files.

Data Files
Labeling List File *Moved*

Please note that this file has been moved to https://postalpro.usps.com/operations/labeling-lists/changes-september-2025. We apologize for the inconvenience. 

Data Files
Address Matching System (AMS) Congressional Table

This document lists congressional district codes for the AMS database.

Data Files
Address Information System (AIS) ZIP Code™ Record Description

File layout for AISUADDR.txt and AISUZIPS.txt.