Here is the test item I created, done under Transaction Line Field:

I have attempted to follow the directions above but have not been successful. "Invoice Group" is not an option in the Custom→Transaction Forms listing, it's only in the "Entry Fields" listing. I have attempted to create the custom field in the detalis listing, but have not had success sourcing it from the invoice line…

Thanks, Lyka. I've used this process to source other data, but I'm really focused on GROUPED INVOICES. I am unable to source/display the individual invoice line items on the GROUPED INVOICE custom form.