Hi Ken,
Just saw your posting now - it didn't display in the list of posted questions, probably something to do with that groundhog...
In the specification, there is a separate Advice Detail section that applies to Cash Invoices as compared to Payments. The fields that you may print within the Cash Invoices detail section are limited to disbursement information such as GL account or amount.
There are a number of fields you may want to print (such as the Cash Invoice number or other 'header' fields), and these can be found within the section called Company Information on the Specification Codes list screen. These fields would be appropriate to print on the advice header or footer, rather than the detail section. Specifically, codes M14-M20 are the fields that can be entered directly on a manual check Payment or Cash Invoice.