@ShiellaGraceA ,

Now I see. I was editing the Invoice template in the final print format. I didn't realize that @SashaMC's instructions involved adding fields to the Screen side of an Invoice. (I'm still learning.) It's cool that you can pass data through a field that way, although I think I'll stick with using the Account # since I can enter it once for each customer and reuse it until the software gets patched. Thanks for the helpful info with screenshots and thanks for sending the bug report to Dev.
You have a lovely day too.