32 C.F.R. § 37.560
(a) To use a fixed-support TIA, rather than an expenditure-based TIA, you must have confidence in your estimate of the expenditures required to achieve well-defined outcomes. Therefore, you must work carefully with program officials to select outcomes that, when the recipient achieves them, are reliable indicators of the amount of effort the recipient expended. However, your estimate of the required expenditures need not be a precise dollar amount, as illustrated by the example in paragraph (b) of this section, if: