Determining Incentive Fee

I am evaluating target costs vs actual costs to determine if the contractor earned any incentive fee. The contract requires that the contractor collect money on behalf of the Govt. The monies collected by the contractor are included a a credit on the public vouchers wtih a total net costs billed on the voucher.

Should the net amount of the voucher (including the credit) as the amount to be used in my incentive fee evaluation?