1st question:
How can we split up an invoice over 3 aging periods?

2nd question:
Is it possible to add the Average Days to Pay field in the Letter/ Statement Designer?

Adagio Receivables 8.1A (070920)

Invoices cannot be split up into multiple due dates. You will need 3 separate invoices, each having a different due date.

I can forward your suggestion for Average Days to Pay field to be added as an available choice for the Statement Designer. Currently this field, nor many of the other period/activity statistics, can be added to statements or letters.

It won't be added to the 8.1 designer though. We're only making improvements to the current versions of the applications.