48 CFR 33.208: 33.208 Interest on claims.

(a) The Government shall pay interest on a contractor's claim on the amount found due and unpaid from the date that—

(1) The contracting officer receives the claim (certified if required by 33.207(a)); or

(2) Payment otherwise would be due, if that date is later, until the date of payment.

(b) Simple interest on claims shall be paid at the rate, fixed by the Secretary of the Treasury as provided in the Disputes statute, which is applicable to the period during which the contracting officer receives the claim and then at the rate applicable for each 6-month period as fixed by the Treasury Secretary during the pendency of the claim. (See the clause at 52.232-17 for the right of the Government to collect interest on its claims against a contractor).

(c) With regard to claims having defective certifications, interest shall be paid from either the date that the contracting officer initially receives the claim or October 29, 1992, whichever is later. However, if a contractor has provided a proper certificate prior to October 29, 1992, after submission of a defective certificate, interest shall be paid from the date of receipt by the Government of a proper certificate.