Current functionality only allows a single "active" set of automatic charges, regardless of delivery date.

By making automatic charges date effective, users would be able to plan ahead and configure the system well in advance of known charge changes. Purchase orders entered today with a delivery date of 6-months from now would pick up the most accurate automatic charges (line and header).

This is especially valuable for companies that plan purchases months in advance but know charge rates will change in the future (i.e. freight rates changing with a supplier). This could work on AR side as well.