Hello professionals, We have a CPFF subcontract, which is a 3-year base and one option year. The base ended in December 2018 and we are in the midst of implementation of the option year. The prime has informed us that the client is imposing a performance-based fee payment structure on Yr 3 (which is complete at this point) as well as the option period. The original fee in our contract is set at 5% and we have been billing it at 5% of incurred and invoiced costs per month (which is the norm). I've been searching through FAR but haven't successfully found any regs we can put behind our pushback and further negotiation with the prime. Any ideas? I think we are fine for the base period to be tied to performance, but I don't understand how this can be imposed on a period that is completed before we were informed of this change.