In this step, you define partial invoicing plan types by specifying the relevant control data for each desired instance.
For each partial invoicing plan type, you can
store a reference plan (for the definition of the reference plan, see the step
"Maintain date proposal for partial invoicing plans").
In PO processing with this invoicing plan type, the dates are taken from this
reference plan, revised on the basis of the current rules, and inserted into
the invoicing plan.