The fundamental difference between an expenditure-based and fixed-support TIA is that:
(a) For an expenditure-based TIA, the amounts of interim payments or the total amount ultimately paid to the recipient are based on the amounts the recipient expends on project costs. If a recipient completes the project specified at the time of award before it expends all of the agreed-upon Federal funding and recipient cost sharing, the Federal Government may recover its share of the unexpended balance of funds or, by mutual agreement with the recipient, amend the agreement to expand the scope of the research project. An expenditure-based TIA therefore is analogous to a cost-type procurement contract or grant.
(b) For a fixed-support TIA, the amount of assistance established at the time of award is not meant to be adjusted later if the research project is carried out to completion. In that sense, a fixed-support TIA is somewhat analogous to a fixed-price procurement contract (although ``price,'' a concept appropriate to a procurement contract for buying a good or service, is not appropriate for a TIA or other assistance instrument for stimulation or support of a project).