What are the proper authorities do use on a contract closeout mod? I was told 43.103 was not appropriated.
It depends on what you are trying to do for contract closeout and what in the contract you are trying to change, e.g. deobligate excess funds from a CLIN etc.
If no physical change to the contract is required then no modification is needed, you are closing out the contract file. In this case you follow the instructions at FAR 4.804-5, DFARS 204.804 and DFARS PGI 204.804.
Back to the “if the modification is to deobligate excess funds” scenario; then the authority could be found in the payments clause(s) you have on the contract. Almost all payment clauses state the government will pay for work “accepted”. If there are excess funds on a contract that typically means that work was not done or accepted. Or it could mean there was an underrun on a CR or Incentive type contract and there it would be the Incentive Fee or Incentive Price Revision Clauses (FAR 52.216-10, and FAR 52.216-16 respectively).
What is unique about a CPFF contract is that there is very limited authority to unilaterally deobligate excess funds under FAR 52.216-7 Allowable Cost and Payment. I answered a closeout question regarding that about 8 months ago here in AAP, you can find in the Contracting answers.
If you do need to modify the contract for a reason other than deobligating excess funds; it is probably something associated with one or more of the items listed at FAR 4.804-5(a) and almost all of those have a clause associated with it for you to cite as the authority on your SF 30 an example would be disposition of government property and you could use the Government Property clause as your authority.
A phone call with the question submitter revealed the modification was needed to get the contractor to sign a “Statement of Release” (See FAR 43.204(c)), which was a local policy. Normally the statement of release is associated with the changes clause. The government either issued a unilateral change order or they could have done it bilaterally. Either way, if a final statement of release is desired for closure only and not because of a change order; then the only recourse is to use a bilateral modification (block 13.C of the SF 30) and use “mutual agreement of the parties” (see FAR 43.103(a)(3)). This is because there is no other authority, contract clause, that has the statement of release language.