What is CASS?

If you’re familiar with address data, consumer marketing lists, or the US postal system, you’ve probably dealt with CASS, or The Coding Accuracy Support System. From a ten-thousand-foot view, the USPS’s CASS certification takes a poorly formatted (or erroneous) address and translates it into a standardized and deliverable format. In doing so, it also corrects any errors and spits out a report about what mistakes it found. The process of running an address through CASS is called “CASS Certification.” Let’s take a closer look…

Coding Accuracy Support System


Here is an example of CASS Certification.

Amazon’s headquarters is located at:

410 Terry Ave N

Seattle, WA 98109


However, if you were to mail a letter to them at:

410 Terrey Avenue North

Unit 123

Seattal, washington 98109


Then you might be surprised to learn that your letter would still arrive at its destination. How does that happen? CASS to the rescue!

The post office’s processing centers use CASS to correct the spelling of “Terry”, change “Avenue” to its standardized form of “Ave”, remove the erroneous “Unit 123”, correct the spelling of “Seattle”, and change “washington” to the standardized “WA” abbreviation.


The postal service processes 421 million pieces of mail per day. Yes, per day! That’s a lot of mail. If a broken address (like the one in our example) required hands-on intervention at the post office, they would be inundated with undeliverable mail.


Aside: Just how bad would it be? Assuming it took 30 seconds of manual labor to correct each address, if just .01% of the letters were incorrectly labeled, it would still take 110 eight-hour shifts per day to sort through them all.

Let’s dig deeper!


CASS Data Points

You might be asking yourself, what information is given during the CASS Certification process? Does it just reformat ugly addresses? Not quite. There’s actually a lot of useful data points that we can extract from CASS. Here’s a short list that might help put things into context:

  • Standardized directions (N, S, E, W, SW, etc.), suffixes (Ave, St, Rd, etc.), and unit designators (Ste, Apt, Unit, etc.)
  • Corrected spellings for street names, cities, states, and other elements
  • Preferred city names
  • County
  • Latitude and Longitude (down to Zip+4 centroid)
  • Voting districts
  • Zoning classification (business, residential, MFDU)
  • Time zone
  • Vacancy Indicators
  • Barcode
  • And match indicators (explaining how closely the input address has matched to the output address)


That’s a lot of data! How is it used, though?


Use Cases

Maintaining Customer Data

What about customer onboarding? How many times have you filled out your shipping information on a website, only to have it tell you, “You entered ____ however we found a preferred address of ____.” You better believe that’s CASS! Now your Amazon package won’t get lost on its way to your house.


County Lookups in Background Screening

The usefulness of CASS goes beyond mail deliverability. It’s used in all corners of the data industry. Remember back in 2022 when we wrote about SSN Traces in the background screening space? If a job applicant doesn’t provide you with a county name in their street address (most don’t), you’ll need a good way of looking that up. CASS to the rescue, yet again.


Reverse Address Lookups

When you have a database of hundreds of millions of individuals, you’ll inevitably want to provide reverse address-lookup services to your customers. The customer might give you an address, you’ll match it in your database, and then return a list of occupants, previous occupants, and even neighbors.

If you don’t validate the input address or if you don’t have standardized formats in your database, it’s very hard to do a string match between the two. “123 East Main Street Unit B” is never going to match “123 E Main St Apt B” – so you must standardize the formats on both sides of the comparison. This ensures that you’re going to get high-quality results in your searches without missing any matches.


Emergency 911 Services

Ever wonder how the fire department or police know exactly where to go during an emergency? Sure, they have GPS in their vehicles, but that only gets you so far – and we’ve all been led astray by google maps before… CASS (more precisely, CASS + SuiteLink) helps emergency services find the correct unit within a complex. Very important when lives are on the line!


Wrapping Up

As you can see, there are hundreds of applications for CASS Certification – many more than we mentioned here. CASS saves the USPS lots of manual work, ensures your mail goes to the right location, and aids the data industry behind the scenes in nearly every product they offer.

If you’re looking to validate addresses, do reverse-lookups, or if you just want to talk about data, send us a message! Our sales associates are eager to chat and learn about your CASS applications.

The authors of the information presented on this page are not attorneys nor are they affiliated with attorneys. The information presented on this page does not constitute legal advice. Before acting on any of the information obtained from this page or any others on this website, please consult your own legal counsel.
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