CASS™

The CASS™ certification process is designed in cooperation with the mailing industry to improve the accuracy of postal codes, i.e., Five-Digit ZIP Code®, ZIP + 4®, delivery point (DPCs), and carrier route codes that appear on mailpieces.

Who is CASS™ for?

CASS™ certification is available to all software developers, mailers, and service bureaus who wish to evaluate the quality of their address matching software. Any mailing claimed at an automation price must be produced from address lists properly matched and coded with CASS-certified address matching methods.

First Class Mail

First Class Mail

Parcels

Parcels

Periodicals

Periodicals

Software Developer

Software Developer

Description

What is CASS™?

The CASS™ software certification program provides hardware and software developers, service bureaus, and commercial mailers a common measure by which to test the quality of address-matching software. Software tests for CASS™ certification are graded by the U.S. Postal Service®, Addressing and Geospatial Technology (AGT) office and the results are returned to the developer to provide useful diagnostics for correcting software deficiencies. However, CASS™ processing does not measure the accuracy of ZIP + 4, delivery point, Five-Digit ZIP Code, or carrier route codes in a mailer’s address file.

CASS™ enables the Postal Service™ to evaluate the accuracy of address matching software programs in the following areas.

  • 5-digit coding
  • ZIP + 4/ delivery point (DP) coding
  • Carrier route coding
  • DPV® or DSF
  • LACSLink®
  • SuiteLink®
  • eLOT®
  • RDI™

CASS™ allows developers, vendors, and mailers the opportunity to test their address matching software packages, and after achieving a specified percentage of compliance to be certified by the Postal Service. CASS™ enables mailers to measure and diagnose internally written, commercially available address matching software packages. The effectiveness of service bureaus' matching software can also be measured.

How does CASS work?

There are two stages in the CASS process:

Stage 1: CASS Test With Answers (optional)

The CASS™ Stage I file is a self-test that helps developers measure and diagnose the performance of their address-matching software when it is applied to a CASS™ test address file. The Stage I results assist developers with software debugging and troubleshooting in preparation for Stage II of the CASS™ certification process. The Stage I file contains approximately 150,000 test addresses extracted from the City State and ZIP + 4 files with samples of all types of addressing used around the country. Some test addresses have been changed for test purposes, and not all records have valid ZIP + 4 codes or valid addresses.

Customers can evaluate the accuracy of their address-matching software by applying the correct carrier route, Five-Digit ZIP, ZIP + 4 codes, DPV or DSF2, LACSLink and SuiteLink elements and by comparing the applied codes with the correct codes provided by the Postal Service. The results of Stage I processing are not reviewed by the Addressing and Geospatial Technology (AGT) office and have no effect on CASS certification.

Stage 2: CASS Test Without Answers (required for certification)

CASS™ Stage II files are used to test the address matching software performance by processing a test address file that is returned for evaluation by the CASS™ Department. The CASS™ Stage II file contains approximately 150,000 test addresses that are extracted and presented in the same makeup and mixture as Stage I without answers. Customers use their address-matching software to apply the correct data applicable to the test record.

Match rates using CASS™ Certified software vary greatly depending on address hygiene, the quality of addresses used, and the timeliness of the customer database update applications. An address with an incorrect Five-Digit ZIP Code, ZIP + 4 code, carrier route code, ZIP + 4 or an address with no ZIP + 4 code or failure to process using DPV or DSF2, LACSLink and SuiteLink elements can contribute to delays in processing mail.

To achieve CASS™ certification, participants must pass with a minimum score of 98.5 percent for ZIP + 4, carrier route, Five-Digit ZIP and LACSLink, 100 percent for delivery point coding, eLOT, DPV or DSF2, RDI and Perfect Address. CASS™ certification is valid until the end of the current certification period. To remain CASS™ certified for each required certification period, developers must reapply for certification and meet the minimum accuracy requirements during Stage II testing.

Maintaining Certification

CASS™ certification is valid until the end of the current biennial period. For software to remain CASS™ Certified for each biennial period, developers must reapply for certification and meet the minimum accuracy requirements during Stage II testing.

Featured Resources

Contact Lists
04/20/2023
CASS™/MASS™ Certified Products Guide - All Sections Data Files Cycle N - (Expires July 31, 2023)

This document contains the certified vendors list for CASS™ and MASS™ products for Cycle N.

Contact Lists
06/20/2024
CASS™/MASS™ Certified Products Guide - All Sections Data Files Cycle O - (Expires July 31, 2028)

This document contains the certified vendors list for CASS™ and MASS™ products for Cycle O.

Applications/ Forms
03/20/2023
CASS™ Order Form

This docoument contains the order form for CASS™.

Tech Guides
03/19/2024
CASS™ Technical Guide for Cycle O

This document provides a technical guide for the CASS™ product. The CASS certification process is designed in cooperation with the mailing industry to improve the accuracy and deliverability of addresses for mail qualifying for postal discounts.

Tech Guides
02/16/2018
CASS™ Technical Guide for Cycle N

This document provides a technical guide for the CASS™ product. The CASS™ certification process is designed in cooperation with the mailing industry to improve the accuracy of addresses for mail qualifying for postal discounts.

Applications/ Forms
12/20/2022
Terms and Conditions for CASS™ Software Developers

This document outlines the terms and conditions for CASS™ certification for developers.

Applications/ Forms
12/20/2022
Terms and Conditions for CASS™ End Users

This document outlines the terms and conditions for CASS™ certification for end users.

Applications/ Forms
12/01/2022
Electronic Product Fulfillment (EPF) Web Access Request Form (PS 5116)

This form is used to create a Web-based account with the Addressing and Geospatial Technology (AGT) office which will be utilized to retrieve/download files from the Electronic Product Fulfillment (EPF) website.

Applications/ Forms
PS Form 3553: CASS™ Summary Report

This form is the CASS™ Summary Report.

Applications/ Forms
03/21/2023
RDI™ Order form

This order form allows customers to order the RDI™ product.

Applications/ Forms
03/20/2023
Z4CHANGE Order Form

This order form is used to subscribe to the Z4CHANGE product. 

Data Files
06/20/2024
Early Warning System (EWS002C0.ZIP)

This file is the EWS production file and is updated weekly. This file contains the Early Warning System data file for the CASS™ and MASS™ certification process.

Contact Lists
04/20/2023
CASS™ Software Manufacturers Data File Cycle N: Certified Products Guide (D) - (Expires July 31, 2023)

This document contains the CASS™/MASS™ certified vendors list for CASS™ software manufacturers for Cycle N.

Contact Lists
04/20/2023
CASS™ Software Manufacturers Cycle N - (Expires July 31, 2023)

This document contains the CASS™/MASS™ certified vendors list for CASS software manufacturers for Cycle N.

Contact Lists
04/20/2023
DPV® Licensees Data File Cycle N: Certified Products Guide (D) - (Expires July 31, 2023)

This document contains the CASS™/MASS™ certified vendors list for DPV® Licensees Data File for Cycle N.

Contact Lists
04/20/2023
DPV® Licensees Cycle N: Certified Products Guide - (Expires July 31, 2023)

This document contains the CASS™/MASS™ certified vendors list for DPV® Licensees Cycle N.

Contact Lists
04/20/2023
DSF2® Licensees Cycle N: Certified Products Guide - (Expires July 31, 2023)

This document contains the CASS™/MASS™ certified vendors list for DSF2® Licensees for Cycle N.

Contact Lists
04/20/2023
RDI™ Cycle N: Certified Products Guide (D) - (Expires July 31, 2023)

This document outlines the CASS/MASS certified vendors list for RDI™ Cycle N.

Contact Lists
06/20/2024
RDI™ Cycle O: Certified Products Guide (D) - (Expires July 31, 2028)

This document outlines the CASS/MASS certified vendors list for RDI™ Cycle O.

Data Files
06/20/2024
Z4 Info File

A downloadable ZIP file containing information related to the Z4 Info File

Tech Guides
04/28/2005

CASS™ Cycle O

Fact Sheets
04/26/2022
TotalDPS – Programmer Specs

This document provides information for calculating TotalDPS.

Announcements
04/26/2022
Modifications to TotalDPS – Programmers Specs file

Changes made to the Total DPS document

Data Files
03/31/2022
CASS™ Cycle O - Stage I File

This file only contains CASS™ Cycle O enhancements.

Data Files
09/07/2023
Data Files
06/10/2022
Stage I Known Errors

The file contains known Stage I errors with a comment at the end of each record.

Data Files
02/04/2022
DPV® & DSF2® Return Codes and Footnote Possibilities

This file contains sample addresses that include the DPV/DSF2 Return Codes and Footnotes.

Fact Sheets
03/31/2023
Tech Guides
03/19/2024
CASS™ Technical Guide for Cycle O

This document provides a technical guide for the CASS™ product. The CASS certification process is designed in cooperation with the mailing industry to improve the accuracy and deliverability of addresses for mail qualifying for postal discounts.

CASS™ Cycle N 2011-2023

Tech Guides
02/16/2018
CASS™ Technical Guide for Cycle N

This document provides a technical guide for the CASS™ product. The CASS™ certification process is designed in cooperation with the mailing industry to improve the accuracy of addresses for mail qualifying for postal discounts.

Presentations
10/10/2014
MASS™ Electronic Testing

This presentation provides information on electronic testing for MASS™.

Presentations
03/30/2010
CASS™ Cycle N Partnership in Tomorrow Presentation

This Partnership in Tomorrow presentation reviews CASS/MASS Cycle M and N requirements.

Fact Sheets
03/30/2010
CASS™ Cycle N Partnership in Tomorrow Minutes

The Partnership in Tomorrow Meeting was hosted by the National Customer Support Center in Memphis, TN with attendees and webinar participants from various industry representatives.

Fact Sheets
Unique ZIP® Code Flowchart

This flowchart describes the logic flow for Unique ZIP codes.

Fact Sheets
Unique ZIP® Code Matrix

The Unique ZIP Code Matrix displays Carrier Route ID, Record Type, and Delivery Point assignment rules within unique ZIP codes only.

Data Files
12/03/2010
CASS™ Cycle N Stage I File

This zip file is for categories only processed with 2009-2011 Cycle N static data.

Data Files
07/16/2010
Early Warning System (EWS) Cycle N Static Data

This zip file contains Early Warning System Data for Cycle N.

Data Files
07/08/2010
R9 RDI™ Cycle N Static Data

This zip file contains RDI 9-digit static data.

Data Files
07/08/2010
R11 RDI™ Cycle N Static Data

This zip file contains RDI 11-digit static data.

Data Files
07/13/2010
Delivery Type Cycle N Static Data

This text file provides delivery type Cycle N static data

Related Products

MASS™

The MASS™ certification is an extension of the CASS™ system, which is a process designed in cooperation with the mailing industry to improve the accuracy of postal codes that appear on mail.

ZIP + 4® Product

The ZIP + 4® Product is a base reference file that can be accessed by an application to assign the correct ZIP + 4® Code associated with a physical address.

RDI™

Business or residential? Make informed decisions, improve your deliverability, and optimize operational efficiency with RDI™.

LACSLink®

The LACSLink® product offers an automated method of obtaining new addresses after a 911 emergency system has been implemented.

SuiteLink®

The SuiteLink® product enables customers to provide improved business addressing information by adding known secondary (suite) information to business addresses, which will allow USPS delivery sequencing where it would not otherwise be possible.

Enhanced Line of Travel (eLOT®)

The eLOT product allows mailers the ability to sort their mailings in approximate carrier-casing sequence.

Carrier Route Product

The Carrier Route Product provides reference information needed to apply carrier route codes to addresses for presort postage discounts.

Contact

For more information about the CASS™ certification process, contact us at 800-642-2914 or email cassman.ncsc@usps.gov.