What Is CASS-Certified Address Standardization Software?

CASS Software Explained

Reducing undeliverable mail, decreasing postage costs, delivering mail faster, and increasing USPS compliance are objectives that any organization involved with document printing and mailing tries to meet.

CASS is one of the best programs available to help achieve those goals.

This blog breaks down the basics of the program, before moving into how it works and how CASS-certified address standardization software can reduce undeliverable mail at your organization.

 

CASS: The Basics

What Does CASS Stand For?

CASS stands for Coding Accuracy Support System, and the name indicates its purpose: to ensure address data is defined and coded correctly to prevent undeliverable mail.

In layman’s terms, this means that this software checks and formats addresses so the USPS’s sorting systems know exactly where each piece of mail should go.

What Is CASS?

CASS is a USPS program that sets measurable standards for translating written addresses into the postal routing codes the USPS uses to sort and deliver mail at scale.

Those standards are applied using CASS-certified software. These software programs format addresses according to USPS rules and assign zip code-related data.

They also parse address elements, resolve them against USPS reference data, and apply routing codes such as ZIP+4, delivery point, and carrier route information that enable automated processing.

What Does It Mean for Software to Be CASS-Certified?

Software that meets USPS accuracy thresholds through formal testing is designated as CASS-certified.

Certification indicates that the software has been evaluated against USPS test files and achieved required accuracy rates across multiple coding categories.

Certification is time-limited and must be renewed to remain valid.

CASS does not guarantee delivery, nor does it replace other address quality or compliance processes. Instead, it functions as a foundational control within address processing.

The program helps mailers and mail providers consistently code address data to USPS standards, allowing for downstream operations such as move update processing, presorting, and production to operate on reliable, standardized inputs.

In other words, if you can’t trust that your data is in the format that the USPS needs, the foundation of your mailing is built on unsteady ground. CASS-certified address standardization software is one of the tools that experienced mail partners, like D4 Solutions, use to reduce errors and make the mailing process more stable.

Do I Need to Use CASS-Certified Software in Order to Obtain Discounts?

Yes. The use of CASS-certified software to confirm the address accuracy of your mailing lists is a requirement to obtain certain discounts from the USPS. 

Why Was CASS Created?

Inaccurate zip codes cause a host of problems in the mailing process, both for the senders and for the USPS itself.

Zip codes are a key part of the USPS’s automated systems, and they’re what tell the USPS, “this is the exact location I need this mailpiece to go.”

If a zip code is erroneous, the USPS has to determine the destination of the mailpiece manually.

This takes up employee time that could be spent on more productive matters, and it leads to delays in delivery that inconvenience customers.

CASS was designed to solve this problem. As the USPS attests, CASS was created to reduce errors in zip codes, delivery point codes, carrier route codes, and other codes that tell the USPS the end location of mailpieces. The standards that make up this program were developed in collaboration with mailing industry peers.

What Does CASS-Certified Software Do? A Complete Breakdown

The USPS provides a simple checklist of every area that CASS address standardization software is evaluated on. We’ll go in-depth on individual points throughout this section, and we’ll also discuss how improving the effectiveness of each item helps you send mail quickly and accurately.

Right now, for your convenience, this is the list of the processes that address standardization software is evaluated on under CASS:

• 5-digit coding.
• ZIP+4/delivery point (DP) coding.
• Carrier route coding.
• DPV or DSF2.
• LACSLink.
• SuiteLink.
• eLOT.
• RDI.

5-Digit Coding

CASS software is evaluated on its ability to correctly assign a valid 5-digit zip code to an address.

This code identifies the general delivery area and serves as the first routing decision point for USPS sorting equipment.

Accurate 5-digit coding directs mail to the correct regional processing facility.

If this coding is missing or incorrect, mail may require manual handling or be routed to the wrong geographic area, increasing processing time and cost.

This is the least granular level of coding evaluated. It is also the foundational layer, and more advanced coding cannot occur without it.

ZIP+4 and Delivery Point (DP) Coding

ZIP+4 coding extends the base 5-digit zip code by identifying a much smaller delivery segment, such as a specific block, floor, or group of addresses.

Delivery point coding indicates the individual mailbox or receptacle to which mail is delivered, such as a specific apartment, suite, or business location.

CASS address standardization software is evaluated on its ability to correctly assign both the ZIP+4 code and the two-digit delivery point code, which together identify the exact delivery location within the USPS delivery network.

This level of coding further reduces the likelihood that mail is marked undeliverable.

Carrier Route Coding

Carrier route codes identify the specific route a postal carrier follows to deliver mail.

CASS address standardization software is evaluated on whether it can correctly assign these codes based on standardized address data.

Having accurate information on the route a mailpiece will take removes complexity on the USPS’s end.

DPV (Delivery Point Validation) / DSF2

DPV, which uses USPS Delivery Point Validation data from the Delivery Sequence File (DSF2), determines whether an address represents a deliverable location according to USPS records.

This evaluation helps confirm that the delivery point actually exists and is recognized by USPS.

USPS testing under CASS measures how accurately software applies DPV results, including identifying addresses that are missing, that required secondary information, or that do not correspond to active delivery points.

This helps prevent undeliverable mail, for clear reasons; if the address you’re sending a mailpiece to doesn’t exist, your mailpiece won’t be able to be delivered there!

LACSLink

LACSLink addresses changes resulting from local government actions, such as rural route conversions or emergency 911 address updates.

CASS address standardization software is evaluated on its ability to identify outdated addresses and convert them to their current equivalents.

This capability helps prevent mail from being sent to addresses that are no longer valid in their original form, even if they were once deliverable.

Without LACSLink processing, addresses affected by these changes may appear correct when they enter the mailstream, but turn out to be undeliverable.

SuiteLink

SuiteLink supports more precise delivery for business addresses by appending missing secondary information, such as suite or unit numbers, when available in USPS data.

Accurate suite-level data improves delivery reliability in multi-tenant buildings and reduces delays caused by incomplete addressing, particularly in commercial mailings.

eLOT (Enhanced Line of Travel)

eLOT assigns sequence and sort order information based on carrier delivery paths.

To put it in a different way, it tells the postal carrier the order in which they should deliver mail.

RDI (Residential Delivery Indicator)

RDI identifies whether an address is classified as residential or business.

This distinction affects postage calculations, surcharge eligibility, and operational planning.

Inaccurate RDI classification can lead to pricing errors and downstream reconciliation issues.

How Does the CASS Certification Exam Work?

The USPS summarizes how the test works here, but, in summary:

• The CASS exam is completed in two stages.
• In Stage I, vendors or users can request a test file that includes the correct answers. This file contains a large sample of fabricated addresses drawn from across the country, many of which include missing elements or intentional errors. Because the answers are provided, Stage I lets developers self-assess and debug their software before formal testing.
• In Stage II, the actual certification test is administered. Participants receive a similar test file without the correct answers and must process it using their address matching software.
• Once processed, the results of Stage II are returned to the USPS for scoring. The USPS analyzes the output, compares it to expected results, and determines whether the software meets the accuracy criteria required for certification.

 

How Does CASS Address Standardization Software Benefit Print and Mail Operations?

CASS-certified software provides measurable value to print and mail operations by confirming that address data is standardized, complete, and correctly coded before it enters production workflows.

It thus reduces errors that can disrupt printing, sorting, and delivery.

This reliability helps organizations avoid costly reprints, returned mail, and postage adjustments caused by undeliverable or misrouted items.

It also helps organizations reduce delays in delivery caused by the USPS having to manually sort mail with incorrect address information.

CASS certification offers a clear signal that software can consistently produce USPS-recognized address data. That’s why it’s required to obtain certain discounts.

What Role Does CASS Play in Compliance-Driven Workflows?

By validating addresses against USPS reference data, CASS-certified software provides a verifiable record that mailpieces are coded correctly, reducing the risk of undeliverable mail.

In other words, using this program helps organizations deliver mailpieces where they need to go, every time. Organizations in highly regulated industries are often required to deliver their documents by a certain time, and so making use of tools that help them do so is important.

How Does CASS Pair with NCOA?

The National Change of Address (NCOA) system helps further confirm the accuracy of addresses in a mailing list.

NCOA identifies whether recipients have moved and provides updated address information.

Regularly using the NCOA helps you get your mail to your customers and clients, even when those clients no longer live at their old addresses.

CASS and NCOA are complementary tools. CASS standardizes and validates addresses, while NCOA helps you confirm all addresses are current.

Together, they help organizations achieve higher mail quality and reduce costs.

How Is CASS Implemented by a Print and Mail Partner in Practice?

At D4 Solutions, we pride ourselves on getting your documents where they need to be, as seamlessly as possible, every time.

That’s why we offer CASS and NCOA services to our clients.

Here’s how it works at D4:

• We use CASS-certified software and NCOA to identify errors in your address list that could cause your mail to be marked undeliverable.
• Then we return your original data files to you, along with a list of the updates to make in order to remove outdated addresses and standardize your records.

Across 45 years of print and mail experience, D4 Solutions has developed processes that meet the needs of clients across industries. Our 99.99% excellence rate in terms of quality and on-time delivery, along with our HIPAA and SOC 2 Type II audited workflows, deliver your mailpieces securely, accurately, and on time.

If you’re looking for an outsource print and mail partner, we can help. Reach out now to learn more.

 

Frequently Asked Questions About CASS (Coding Accuracy Support System)

1. What is CASS in printing and mailing?

 

CASS, or the Coding Accuracy Support System, is a USPS certification program that evaluates address validation and standardization software.

It helps organizations update their mailing lists so that addresses are accurate, deliverable, and formatted according to USPS standards, which can reduce undeliverable mail.

2. Why is CASS-certified software important?

 

These software programs help your organization:

• Qualify for USPS mailing discounts.
• Improve delivery success rates by verifying and standardizing addresses.
• Integrate automated address verification into printing and mailing workflows.

3. How does CASS certification work?

 

The USPS evaluates address standardization software by comparing its output against a master address database.

Software that consistently corrects, standardizes, and validates addresses earns certification.

4. Can CASS-certified software verify addresses for every type of mail?

 

Yes. It can validate residential, business, and P.O. box addresses, and can also handle specialized formats like APT, STE, and rural route addresses.

It does not guarantee 100% deliverability, but it can significantly reduce mistakes.

5. How does CASS help reduce mailing costs?

 

By standardizing and correcting addresses, this software:

• Minimizes undeliverable mail, and the time and monetary costs that come with it.
• Allows you to qualify for certain postage discounts.

6. What is the relationship between CASS and NCOA?

 

CASS finds errors with address formatting, while NCOA (National Change of Address) updates addresses when recipients move.

7. Should I use CASS-certified software?

 

If you’re sending mailings that need to be delivered on time, then we would recommend using CASS-certified software can help you achieve this goal. Without it, you run the risk of incurring delays and costs due to undeliverable mail.

8. Who should I partner with if I need CASS services for my mailings?

 

If you’re looking for a print and mail partner that offers CASS services, while being committed to security, accuracy, and on time delivery, D4 Solutions is a good match for you.

Our HIPAA and SOC 2 Type II audited workflows have a 99.99% accuracy rate in terms of quality and on-time delivery, and our print and mail experience across industries gives us the insight to make your mailing processes as efficient as possible.

Reach out now to learn how we can optimize your workflows!