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CASS Certification for USPS Bulk Mailing

Scott HochbergScott Hochberg
 Postage $aver Software


The length of time you can re-use a CASS-certified list is changing. Here's how CASS requirements are changing.

Mailers who are sending bulk mail can save additional postage and avoid the $275 Annual Mailing Fee by adding barcodes. But to get the discounts, the barcodes must include precise delivery information so the mail can be automatically sorted in the order that it is delivered.

Postal Barcoder Max Creates Perfect Intelligent Mail Barcodes The required information is an accurate zip+4 code plus an additional 2-digit "delivery point code", which is included in the barcode but is not shown in the printed zip code.

To make sure that information is accurate, USPS requires you to have your mailing list checked against the master list of USPS addresses before you create the barcodes.

The software that checks your list against the master is called "CASS-certified" software, so checking the mailing list using that software is referred to as "CASS-certifying" the list. Don't worry, most smaller mailers don't actually buy expensive CASS software, but instead use an inexpensive service to take care of CASS for them, as discussed below.

Not sure whether you need to do CASS certification? Check our quick Move Update & CASS checklist.

Here's what this page covers:

red dotHow do I CASS-certify my list?

red dotHow often do I CASS-certify?

red dotWhat if I change a few addresses?

red dotHow does USPS know whether I've complied?

Remember that barcodes are not required for bulk mail discounts. But if you are adding barcodes, or if you are preparing a "carrier route sorted" mailing, you must CASS-certify your list at least as often as USPS requires, even if you are sure that the zip+4 codes have not changed.

And in case you're curious, CASS stands for Coding Accuracy Support System. But fortunately you don't need to remember that.
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How do I CASS-certify my mailing list for bulk mailing?

For small to medium volume mailers, it's generally not practical to CASS-certify your own lists in house, since the software to do this typically costs $800 per year or more. It's expensive because it includes a subscription to the USPS national address data base, which has about 30 million entries. It's not something you want to have to pay for and maintain unless you are doing a lot of bulk mailing.

A better option is to use one of the service companies that will certify your list online. They typically charge less than $2/1000, though some have a minimum job charge.

And, if you are already using a service for National Change of Address (NCOA) processing, you're already getting CASS certification at no extra charge as part of that process.

Here is the company we use for CASS certification when we do a mailing: They are especially good for smaller lists as they do not have a per-job minimum charge.

You just upload your list to them. They run your list through their CASS software, and then return the certified list to you along with the required Form 3553 (aka "CASS report"). Form 3553 proves to USPS that you followed the CASS requirement.

If you're buying a list from a list vendor, it's worth buying from a vendor that provides their lists with CASS certification and NCOA included, so you can skip that step. Most legitimate list vendors will offer certification as part of the price.

If a list processing service or a list vendor claims to offer CASS, but does not provide a Form 3553, then they are not really CASS-certifying your list!

Once you have a CASS-certified list, you don't have to mail to the whole list all at once. So if you know you're going to send, say, 10,000 pieces over the next two months, it ok to have the whole list certified at one time. Then you can pick however many addresses you want to mail to each time as long as the CASS-certification remains valid.

But note, USPS has reduced the amount of time you can use the same list without CASS-certifying again, so be sure to look at the new CASS rule discussed next.

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How often do I have to CASS-certify my mailing list?

CASS rule change effective October 1, 2022!

This change affects you if you have your list CASS-certified or buy a CASS-certified list and then use it more than once without re-certifying it. USPS has changed the length of time that mailers can re-use a CASS-certified list without re-certifying.

If you always CASS certify or NCOA process your list every time you send a presort mailing, then the new rule does not affect you. You can keep doing what you're doing and you will be in compliance.

In the past, the expiration date for a cass-certified list was based simply on the number of days since the list was certified. For most mailers, that meant that you could re-use a CASS-certified list for up to 180 days without re-certifying it. Carrier route mailers could re-use their lists for up to 90 days.

The new rule is more complicated. Instead of being based on when you last had your list certified, the expiration is based on the date of the USPS CASS data file that the CASS vendor (or CASS software) used to certify your list. And the amount of time until CASS certification expires will be much shorter than 180 days.

USPS issues a new CASS data file every month, but CASS vendors are not required to start using the new lists immediately. So the only way you can know the date of the CASS data file they used is to look on the Form 3553 that the vendor (or software) provides when your list is certified. With that, you can use the chart below to know when the CASS certification expires.

To figure out when a file's CASS certification expires, first find the column labeled "Date of database product used", and then the box under it labeled "Zip+4 File".
USPS Form 3553 CASS report
If the month shown is January then the certification expires April 30.
If the month shown is February then the certification expires May 31.
If the month shown is March then the certification expires June 30.
If the month shown is April then the certification expires July 31.
If the month shown is May then the certification expires August 31.
If the month shown is June then the certification expires September 30.
If the month shown is July then the certification expires October 31.
If the month shown is August then the certification expires November 30.
If the month shown is September then the certification expires December 31.
If the month shown is October then the certification expires January 31.
If the month shown is November then the certification expires February 28/29.
If the month shown is December then the certification expires March 31.

Eventually, all of this information will be shown on the form, but vendors are not required to do that until late in 2023.

The good news is there are services that don't currently charge a minimum job charge for CASS-certification, so you pay only for what you use. That can help if you now have to CASS-certify more often than in the past.

If you add an address to the list, or change a street address, that address is no longer CASS-certified. You can either re-certify the entire list, or, if it's easier, you can manually look up the new address as explained next.

Can I just change a few addresses without paying to CASS-certify the whole list again?

Yes. If you correct or change a few addresses on your mailing list, you can manually look up the zip+4 and delivery-point codes that you need. USPS allows this for "manually maintained lists or small computerized lists".

Go to the USPS zip code finder, choose the "by address" option, and enter the address. Be sure to enter any directionals (like N, S, E or W) and unit numbers or apartment numbers.

When you find the correct listing, click the down arrow to the right of the address. You'll see detailed information for the address, including the delivery point code.

If the USPS site cannot identify an address, or gives you multiple addresses to choose from, then you should contact the recipient for the correct address, or send the piece with a regular stamp. You should not include nonbarcoded pieces in a barcoded bulk mailing, especially if USPS has waived your annual permit fee, as including too many nonbarcoded pieces will cause your fee waiver to be cancelled.

How does USPS know whether I've CASS-certified my list?

If you are claiming a discount for barcoding your bulk mail, USPS may ask you for a Form 3553 (aka "CASS report") when you submit your mailing. Form 3553 is used to prove that you have CASS-certified your list within the required time period.

Form 3553 CASS Report Form 3553 is printed by the software that is used to CASS-certify your list. It's not a form you fill out manually. If you purchase a list from a vendor who claims the list is CASS-certified, you should expect them to provide a Form 3553. Same goes for a vendor who CASS-certifies a list for you.

USPS will not always ask for Form 3553, but if they request it, you must provide it or your mailing will not be accepted at barcoded rates.

Where to show the CASS date on the postage statement You must also enter the date you had your list CASS certified on the postage statement you submit with your mailing (or on the USPS Postal Wizard if you are submitting the postage statement electronically). When you sign the form, you are declaring that the information on the form is accurate, so we do not recommend entering a false date.

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Scott Hochberg
Scott Hochberg started Postage Saver Software in 1994. He's been helping small businesses and nonprofits save postage with postal bulk mail for more than 25 years. Scott's based in Austin, Texas. He's happy to answer your bulk mailing questions!