12 CFR 412.11: Payment guidelines.

(a) Payments from a non-Federal source, other than payments in kind, shall be by check or similar instrument made payable to Eximbank. Payments from a non-Federal source, including payments in kind, are subject to the maximum per diem or actual subsistence expense rates and transportation class of service limitations prescribed in 41 CFR chapter 301.

(b) If Eximbank determines in advance of the travel that a payment covers some but not all of the per diem costs to be incurred by the employee, Eximbank shall authorize a reduced per diem rate, in accordance with 41 CFR part 301-7.12.