Claims by a contractor after the final payment

Dear Members,

The civil contractor during the performance of the contract submits the claims on its incremental cost impact in lieu of changes in minimum wages. It is an item rates contract. Can it be honoured ? If so he did not raises the claims within the stipulated time frame ( immediately as per the contract ) from the event of occurance of the changes in the law. Request the feedback and suggestions from the honourable members.

Thanks

Anantha