How should contractors identify payments as IFF if they are paying by check?

Contractors should follow the instructions in the IFF Clause, 552.238-74, and must provide the following information with all payments: contract number(s)), report amount(s)), and report period(s)). If the payment is for more than one contract and/or for multiple reporting periods, the specific amount to be allocated to each reporting period and each contract number must be included on any check submitted