The prompt payment rules count from two events. One is the 30th day after the designated billing office receives a proper invoice 1; the other is the 30th day after Government acceptance of supplies delivered or services performed 2.
The standard Prompt Payment clause makes the due date the later of the two: the due date for making invoice payments by the designated payment office is the later of the following two events 3. A proper invoice sent before acceptance does not make the money due sooner.
Worked example. Contractor H sends an invoice with the wrong contract line item number. The billing office returns it, and Contractor H loses weeks sending a corrected one. Its next invoice matches the contract line by line and goes out the day the government accepts the delivery.
Indented paragraphs are invented worked examples. Tool links open Bids2Bank and need a free account.