What is CASS™? The USPS® Coding Accuracy Support System

USPS CASS certification

CASS stands for The Coding Accuracy Support System (CASS). It's a certification tool created and used by the USPS to ensure the accuracy of validation and standardization software that taps into the USPS database.

There are a number of professional services that tap into the USPS database, like address validation for example. These services tap into the USPS database to serve as a USPS address checker to correct, update or double-check addresses. CASS gives the USPS a way to certify that the responses that service provider gives to its customers are accurate and meet USPS standards.

A CASS certified service provider accurately meets the standards of the USPS, and has their approval. A service that processes addresses according to CASS standards will, at the very least, fill in information missing from an address, standardize it, and update it. Many services (like us here at Smarty, formerly SmartyStreets) will also validate an address by checking to see if it's already in the database.

To become CASS certified the USPS requires that service providers' software uses and LACS when checking addresses.

In this article, we'll cover:

CASS System in Depth

CASS is a system that the USPS uses to qualify specialized software—private party software that references the USPS address database to process addresses. The CASS system gives the USPS a way to evaluate and measure how accurate the results of that private party's software processes are. This means that an address processed by a standardizer or address validator that is using CASS-certified software is more reliable than an address that is not.

There's a little bit of confusion that can pop up when talking about CASS, though. That's because the word "CASS" is a word often used to talk about "CASS certification" and "CASS processing." Both are important parts of the system, and both are probably more directly applicable to you than regular ol' CASS is. Below is the breakdown.

What is USPS CASS Certification?

USPS CASS certification means that a business passed USPS quality control on the subject of standardizing and validating addresses (we'll talk about both below here). It's offered to any organization that wants to test the accuracy of this kind of software. In fact, some businesses have to maintain and renew CASS certification on a yearly basis.

When a business wants to be CASS certified, they show off their software to the USPS. The USPS checks to see if the software meets the standards and follows the procedures required, then gives a yes/no response on the matter.

CASS Certification Requirements

Getting certified is pretty straightforward. There are only two requirements you have to meet in order to qualify for certification: using DPV, and using LACS. Any software that uses both in its address processing services may be certified. Now we're sure you use these acronyms in day-to-day life. But, on the off chance they're unfamiliar to you,we've provided a brief description of both here.

Requirement 1 - DPV (Delivery Point Validation)

DPV, to be succinct, is when you check to see if the USPS can and will deliver to the doorstep of a specific address. We'll talk more about this below, along with validation in general, but DPV is the most specific and accurate version of validation. Anything less accurate won't cut the mustard where CASS is concerned.

Requirement 2 - LACS (Locatable Address Conversion System)

LACS is a database maintained by 911 emergency services to make sure that a location can be found in case emergency services are needed. It keeps track of addresses that have been updated in order to match a national standard, which is used to make finding locations easier in an emergency.

A CASS-certified system must at least reference the LACS system when processing to see if an address has been updated. Preferably, addresses are then updated to the most current version contained in LACS in order to keep records accurate. We'll talk about this more in depth below as well.

What is CASS Processing?

So what all is involved in CASS processing? When a CASS-certified provider runs an address through their software, what is happening? While each provider uses its own specific processes, there are some things that are common to all CASS processing. The three that are important enough to mention here are address standardizing, address updating, and address validation. Feel free to check out the USPS's latest iteration called CASS Cycle O.

Step 1 - Standardization: Cleaning, Correcting, and Completing an Address

When we're talking about address processing, we are always including standardization. Before anything else can be done (list deduplication, address validation, gathering supplemental information, etc.), a list of addresses has to be tidy and organized. The way we make that happen is by standardizing addresses.

Standardizing an address means bringing it into compliance with USPS postal standards. This involves a couple of things. First, addresses are put in the right format:

house number, street name
	city, state ZIP Code

The addressee line is disregarded, since it's irrelevant to the task at hand. Next, accurate abbreviations are added; for example:

123 Sesame Street


123 Sesame St

After that, spelling errors and minor mistakes are corrected. This includes mistakes on the designation of the street/way/lane/road etc. Missing information is also filled in, so long as it can be correctly deduced from what's available. ZIP Codes are commonly filled in, but they can only be done if both the street-level and the city/state-level information is present and accounted for.

It's important to keep in mind that holes can only be filled if there's a way to infer the information from what's available. Neither street name nor house number can be inferred if they're missing. There's just no way of telling where the address is without them.

After all of this is taken care of and the address is all jazzed up, it's ready for any other processing steps that it might need to go through.

Step 2 - Address Updates

As mentioned above, addresses sometimes change, so a CASS-certified system will reference LACS during processing. What is LACS? It's a system that records the changes made to addresses in order to improve the efficiency of emergency services.

Since it was instituted, the 911 system has been slowly reformatting addresses across the country to conform to a national standard, making places easier to find. Originally, addresses were assigned however a local government felt they wanted to do it (usually according to the order in which houses were built). The individuality and originality of each address system (or even specific address ranges within an address system) made responding to emergencies very difficult.

So we started standardizing address assignments—building numbers originating from central locations, evens and odds on separate sides of the street, that sort of thing. Old addresses were updated, changing them to meet the new standards. Now, when new structures are built, they are assigned addresses according to their location on the street.

That way, when the ambulance or fire engine comes rolling down the street, they know where to look to find the place they're headed to.

The problem with updating addresses is that it can mess with mail delivery. Let's say Grandma's home address was 123 Maple Lane, but got changed to 124 because it's on the wrong side of the street. Our letters to dear old Granny will now end up in the twilight zone, instead of reaching her, if we don't modify the address label.

So 911 keeps track of these address changes. They established LACS, which is responsible for tracking the modernization and standardization of addresses across the nation. That database can be accessed and cross-referenced, so that someone sending mail to 123 Maple Lane can have their stuff routed over to 124 Maple Lane, ensuring that Granny still gets your letter. A CASS-certified system checks addresses against LACS, making sure that the address they put on the envelope and give to the postman is the most updated address for that location.

It's important to note that LACS is not the same as NCOA. NCOA stands for National Change of Address, and it's the database that tracks forwarded addresses. In the event that someone has to move from one location to another, the USPS has forms (it can be done online too, now) that you can fill out, telling them who you are, where you currently live, and where you're moving to. That way, when mail addressed to you goes to your old address after you've relocated, the mailman will instead forward it to your new address.

Not everyone forwards to an address when they move, so forwarding addresses aren't always accurate. Beyond that, forwarding addresses have a shelf life, beyond which the USPS expects everyone to know your new address and stops shipping misaddressed mail to you. So NCOA is not the most reliable in regards to keeping track of where a person lives.

Unlike NCOA, LACS doesn't track the "who" of the address, just the "where." Also unlike NCOA, LACS is very reliable. For example, many address validation providers don't use NCOA because of how inaccurate it is; meanwhile, every provider uses LACS when they process addresses, to ensure they are up to date.

Here's how they do it: if there's been a change, the address that was supplied will usually be updated to it's most current state, as recorded in LACS. In the event that it's not updated (some providers choose not to, and it's kind of frowned upon), you will still usually be provided with the most current data, paired with the original address. Barring that, the provider will acquire an accurate, updated ZIP+4 Code for the delivery point, and append it to the address.

Step 3 - Delivery Point Validation

Address validation (sometimes called address verification), is a method of determining if an address is real. It compares addresses against an authoritative database to see if that address is already on file. If it is on file, it's both a real address and an active one, meaning that it's both an actual location, and one that's currently occupied and signed up to receive mail. Addresses that don't have a match in the database are "invalid", for whatever reason, and either cannot or are not receiving mail.

But there are varying levels in accuracy to be had with address validation; some providers don't check the whole address. UPS, for instance, offers address validation, but only checks to see if city "A" contains street "B", and if house number "C" is within the proper ranges for that street. So if Sesame Street has a valid house number range from 101 to 199, 123 will come up as valid for providers like UPS, even if there's no actual structure bearing the 123 address. CASS processing addresses this problem.

What's required by CASS, and what we do here at Smarty, is called Delivery Point Validation, or DPV. This means we check the actual delivery destination, the front door of where the mail is going. We ask the USPS "Do you currently deliver to this location?" and the yes/no response we get is what determines whether an address is valid or invalid.

DPV is also required before the USPS will let us add ZIP+4 information to an address. And to top it all off, DPV will always standardize addresses before checking them, which means you won't just have accurate addresses, you'll also have clean data.

Address validation can be done on international addresses as well, and in these cases, addresses are checked against the primary database in that country (Royal Mail in the UK, Deutsche Post in Germany, La Poste in France—you get the idea). In the US, that authority on mailing addresses is (surprise, surprise) the United States Postal Service, which means that the most accurate way to validate a US address is to use a CASS-certified provider.

Reasons for CASS-Certified Address Processing

There are a number of reasons that using CASS-based software or systems is better than any alternative. First is the accuracy. The services offered via CASS-certified providers are more reliable than from any non-CASS provider. That's because, for all of the services involved in CASS processing, USPS databases and standards must be referenced. Since CASS is the USPS's own sanctioned system, you can't get any closer to having the USPS doing it themselves than choosing a provider with the CASS stamp of approval on it.

In essence, it's the same as the USPS saying "Yup, that's the way we like it done."

In addition to better accuracy, CASS processing is pretty much the complete package. Not counting the supplemental data you mind need gathered on addresses (which could be anything from geocodes to census data), CASS covers everything you would need to do to an address. CASS processors can help you keep your database clean and organized. They can help you keep it updated. They can help you keep it accurate. It's the secret to avoiding bad data.

But beyond making sure you're mailing to the correct address, CASS can save you money in another way. It's called "worksharing discounts," and they're available to any organization that sends mail in bulk.

Here's how it works. Normally, when you buy a stamp and slap it on an envelope, you're paying full price for that postage. That's because the USPS has to sort it, put barcodes on it, and otherwise put it in the right place so it goes where it should. That all adds man-hours they have to pay for, so they make you pay for it via postage. Paying 80¢ for a single letter to be mailed isn't so bad. It starts to become a problem, though, when you have to fire off 1000 of them.

If you're shipping in bulk, you can do both the USPS and yourself a favor by taking some of the work off of their hands. This is the "worksharing" part. You do things like presorting the mail, sometimes even adding the barcodes yourself. To qualify, the USPS also requires that you CASS process your addresses (go figure). That means standardizing them, updating them, and validating them. They need your addresses to be cleaned up, up to date, and accurate, otherwise it will cause problems as they try to deliver it.

Worksharing means that the USPS has to do less work before throwing the mail on the truck. That leaves transporting the mail to be the majority of their work—something they already have to do for the other mail they're carrying. So, since you're saving them the time (and they want you to keep lightening their load), they don't charge you for labor you're not forcing them to perform. This is the "discount" part. Here it is in a nutshell: worksharing means making the job easier for the USPS, so they cut you a discount.

It sounds like a lot to ask, but those with the courage to manage their own mail will be able to obtain the bulk mailing discounts.

Those are some pretty hefty benefits—help with data management, avoiding returned mail, and saving money through worksharing discounts. All of it is made possible through CASS processing.


The Coding Accuracy Support System was designed to make the US mail system both easier to use and more useful. That said, not all CASS certified providers are created equal.

Providers vary in specialty, each one staking a claim in a unique niche. Some offer only basic functionality, doing the bare minimum required by CASS. Others offer remarkably inexpensive service by likewise stripping away extras (and sometimes sacrificing reliability and accuracy). Some go a more expensive route, and collect a wealth of information on every address they process.

As for us here at Smarty? We focus on three things: speed, reliability, and ease of use. We offer the fastest turnaround times in the industry when processing addresses (which includes standardizing, updating, validating, and a handful of very valuable supplementals). We promise an uptime higher than the uptime Google is committed to for their Google Maps API. And you can be using or implementing any of our tools in minutes (like, count-them-on-one-hand minutes).

If you're curious about our services, or just want to learn more about CASS, you can call our direct customer service line, where you'll never have to talk to a machine before being able to talk to a human being. And if you happen to have a question that's too technical for them, then they can shout to our dev team in the next room over, and ten footsteps later you're on a conference call with an industry expert. We like answering questions and solving problems, and if we can't do it, we'll help you find who can.

Then again, you can always verify an address for yourself. We're confident that our CASS-certified software is exactly what you're looking for.

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