22 CFR 1506.5 - Demand for payment.
(a) A total of three progressively stronger written demands at approximately 30-day intervals will normally be made, unless a response or other information indicates that additional written demands would either be unnecessary or futile. When necessary to protect the Government's interest, written demand may be preceded by other appropriate actions under the Federal Claims Collection Standards, including immediate referral for litigation and/or offset.
(b) The initial written demand for payment shall inform the debtor of:
(1) The basis for the claim;
(2) The amount of the claim;
(3) The date when payment is due, 30 days, from date of mailing or hand delivery of the intial demand for payment;
(4) The provision for late payment (interest), penalty and administrative charges, if payment is not received by the due date.