By including a per diem amount in the letter, the parties will not have to execute another payoff letter if the termination date. The payoff letter should also specify a per diem, an additional amount required for each day after the payoff letter is dated.The Payoff Amount and Per Diem Amount quoted herein are effective through December 31, 2020. GSA establishes the maximum CONUS (Continental United States) Per Diem rates for federal travel customers. Unbundling in an inpatient setting is to use a graduated per diem payment in place of the normal per-case payment for the specific cases in which unbundling has.