(2)(i) Contractors must support written demands for additional penalty payments with the following data. The Government must not request additional data. Contractors must—
(A) Specifically assert that late payment interest is due under a specific invoice, and request payment of all overdue late payment interest penalty and such additional penalty as may be required;
(B) Attach a copy of the invoice on which the unpaid late payment interest is due; and
(C) State that payment of the principal has been received, including the date of receipt.
(ii) If there is no postmark or the postmark is illegible—
(A) The designated payment office that receives the demand will annotate it with the date of receipt, provided the demand is received on or before the 40th day after payment was made; or
(B) If the designated payment office fails to make the required annotation, the Government will determine the demand’s validity based on the date the contractor has placed on the demand; provided such date is no later than the 40th day after payment was made.