48 C.F.R. § 42.705
(a) Final indirect cost rates shall be established on the basis of—
(b) Within 120 days (or longer period, if approved in writing by the contracting officer,) after settlement of the final annual indirect cost rates for all years of a physically complete contract, the contractor must submit a completion invoice or voucher reflecting the settled amounts and rates. To determine whether a period longer than 120 days is appropriate, the contracting officer should consider whether there are extenuating circumstances, such as the following:
(c)
(1) If the contractor fails to submit a completion invoice or voucher within the time specified in paragraph (b) of this section, the contracting officer may—
[61 FR 69296, Dec. 31, 1996, as amended at 67 FR 6119, Feb. 8, 2002]