The distributor buys at a standard cost that both parties know is not the real price. When they sell to the specific end customer covered by the authorization, they sell at the negotiated price and submit a debit claim for the difference. The manufacturer pays it, and only then is the true net revenue on that shipment known.
This makes ship & debit unusual: it is not an incentive layered on top of a price, it *is* the price. Revenue recognized at shipment is provisional, and the size of the eventual correction depends entirely on how well claims are validated.
The control that matters is line-level validation — confirming that each claimed line has a live authorization for that part, that end customer, that price and that date, using the partner’s identifiers resolved to yours. Programs that sample rather than validate typically find under 1% invalid; programs that validate every line find 3–7%.