There are a few different types of fixed price contracts
Firm Fixed Price (FFP)
No Adjustments
What you see is what you get
Fixed Price Incentive Fee (FPIF)
The Seller is offered a Performance Incentive
Incentive can be Performance, Cost or Time
Fixed Price Award Fee (FPAF)
If seller exceeds expectations an award
is paid to the seller
Fixed Price Economic Price Adjustment (FPEPA)
The price can be re-evaluated if market
conditions change