I am curious how other banks handle this situation....

Account Title is ABC Inc

Checks deposited are made payable to ABC Inc DBA CDF Mart

We are stamping the checks with our endorsement stamp. We have no relationship with CDF Mart and Secretary of State does not have this company listed as an assumed name. I understand that we would never accept checks made payable to just CDF Mart but shouldn't the stamp be sufficient without having the CDF Mart as part of the title?

Your bank's endorsement guarantees that CDF Mart received the proceeds every check payable to CDF Mart. In order to assure that your guarantee is not foolhardy, you would require documentation to verify that ABC Inc. has the legal right to use that name in its activities; i.e. you need a copy of ABC Inc.'s DBA registration that they are doing business under that assumed name.

The account title is the least of your problems, but it should be accurate so your tellers understand checks payable to CDF Mart can be deposited to ABC Inc.'s account. Otherwise, if you hire an experienced, well trained teller from another bank he or she will refuse the deposit.

The checks are not payable to CDF Mart they are payable to ABC Inc DBA as CDF Mart. The account is only in the name of ABC Inc.

That fact doesn't impact what Mister Dowd suggested that you should do regarding their ability to operate a dba in that name.