Thank you for the reminders. I've been using Lacerte for quite a while and it is amazing what one can forget. I unlocked all clients, ran an updated client database, relocked, and then ran my filters and found more clients, and all that I expected.

To find out what column a form number is (now I remember), I create a filter in Lacerte with a distinctive name, use the form number I'm looking for, exit Lacerte, and then open the CTS###.IW3 (or equivalent) file where ### is your workstation number (which shows up on the bottom of the system information screen when you press F10). Search for the filter you just created (search twice to get to the actual definition of the filter), and you will see the C7_## that the filter is using.