Mailers who are sending bulk mail can get additional discounts by adding barcodes to their mail. The barcodes represent precise delivery information so that the mail can be sorted automatically in the order that it is delivered by the postal carrier. That includes the full 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.

Smart Barcoder Creates Perfect Intelligent Mail Barcodes Since USPS is giving you a discount for providing the barcode, they insist that the zip code and delivery point code be accurate. So, they require 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 people refer to checking the mailing list as "CASS-certifying" the list.

Here's what this page covers:
Barcoding is not required for bulk mail discounts. If you are not barcoding, you generally* don't need to CASS-certify your mailing list.

And, if you are using National Change of Address (NCOA) service to comply with the Move Update requirement for bulk mailing, that process usually includes CASS certification, so you don't need to pay for CASS certification separately.

(*CASS-certification is also required for bulk mailings that are carrier-route sorted. Carrier-route sorting is a type of bulk mailing used to "saturate" an area with mail. Because of its limited use, we don't cover that topic.)

How do I CASS-certify my mailing list for bulk mailing?


CASS Summary Report USPS may ask you for a Form 3553 ("CASS report") when you submit your bulk mailing.

Form 3553 is printed by the software that is used to CASS-certify your list. It's not a form you fill out manually.
CASS is a trademark of the USPS
Technically, "CASS certification" is the USPS' procedure for verifying the accuracy of commercial zip code matching software.

But most mailers and many postal employees think of CASS certification as the actual matching process that the software performs, rather than the postal service's testing procedure.

So, we'll use the common meaning of the term here.
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 if you are only doing small or occasional mailings.

A better option, for most small to medium volume mailers, is to use one of the service companies that will certify your list for you. For a small list, they typically charge around $30. CASS certification is also generally included at no extra charge as part of the National Change of Address (NCOA) service, so if you are already doing NCOA, you don't need to pay anything more for CASS.

Here are some companies that our customers use for CASS certification: 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 a Form 3553 ("CASS report"). Form 3553 shows what software was used to certify your list and when the list was certified. You are not required to submit Form 3553 to the USPS unless they ask for it, but it's a good idea to take it with you in case they decide to ask.

Where to show the CASS date on the postage statement There is also a place on the postage statement where you must indicate the date when CASS-certified matching was done. You must fill in that date on the postage statement if you are submitting a barcoded mailing.

Once you have your list certified, 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 out over the next six months, it pays to have the whole list certified at one time, so you don't pay multiple job charges. Then you can pick however many addresses you want to mail to, for every mailing during that six month period.

If you're buying a list from a list vendor, it's worth it to buy from a vendor that provides their lists with CASS certification and NCOA included. Make sure they provide a Form 3553 with the list if they claim it's CASS-certified.

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

Mailers who are using Intelligent Mail barcodes on their bulk mailings must update the CASS certification for their mailing list at least once every 180 days.

Mailers who are using carrier route sorting must update their CASS certification at least every 90 days.

That means that for barcoded mailings, every address must have been verified using a CASS-certified method no more than 180 days before the mailing is delivered to USPS. Or, for carrier route mailings, no more than 90 days. 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.

Go to the USPS zip code finder 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 you absolutely can't find the zip+4 and delivery point code, 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.