28 C.F.R. § 90.34
Each participating Tribe will receive access to an equal portion of the funds set aside for maximum allowable reimbursements under § 90.33 (e.g., 25 percent of the total funds available for the Tribal Reimbursement Program), unless their prior year expenses were less than the maximum amount, in which case they will be limited to the actual amount of their prior year expenses. Over the course of a calendar year, participating Tribes may draw down funds from the maximum allowable reimbursement as needed for eligible expenses as described in § 90.36 . Participating Tribes are not required to provide documentation at the time they draw down from the maximum allowable reimbursement. Participating Tribes must provide a summary of eligible expenses at the end of the calendar year, which must identify actual expenditures eligible for reimbursement, including dollar amounts for each expenditure and how they were calculated, and must keep documentation on file to support each claimed expense. Such documentation must be sufficient to meet the standards that 2 CFR part 200 provides for grants.
28 C.F.R. §90.34