Based on the situation I have described, It is clear that contractor A is in breach of contract and does not intend to fulfill its acknowledged contractual obligation without government intervention and adverse action. What authority would support the contractor assertion direct billing is allowed on a contract where the PoP is physically complete?
There does not appear to be any precedence or regulation that would explicitly provide for direct billing after a contract is closed out, particularly for something not originally part of the agreement. Submission of a proper invoice requires that the invoice include contract number or other authorization for supplies delivered or services performed (including order number and line item number). In this instance there would not be a line item to reference.
However, there are a number of ways in which a contractor can bring claims to the Government that are not precluded by the ending of the Period of Performance and that don’t require a contract extension.
Under FAR 33.206(a), the contractor can submit a written claim to the contracting officer within 6 years of the accrual. If the contract was awarded prior to October 1, 1995 (the scenario provided indicates this may be possible) there is no time limit as to when the claim can be brought.
FAR Subpart 50.1, Extraordinary Contracting Events, does provide for Contract Adjustments. These include a detailed process for a Contractor to request an adjustment in FAR 50.103-3. There are further requirements provided in DFARS 250.103-3 as well as PGI 250.101-3 and related PGIs. There are no time limits delineated for these actions.
We trust that the solicitation was conducted under FAR 45.201 Solicitation, which in paragraph (b) states that the contractor is responsible for all costs associated with the GFP. That would indicate that Contractor A should have accounted for the rehabilitation costs in their original proposal/bid.
Note that the age of the contract will require a visit to the archives to validate that the clauses included in the original award are still valid or meet the same requirements as the current documentation.