41 CFR 301-52.4 - What must I provide with my travel claim?
You must provide:
(a) Evidence of your necessary travel authorizations including any necessary special authorizations;
(b) Receipts for:
(1) Any lodging expense;
(2) Any other expense costing over $75. If it is impracticable to furnish receipts in any instance as required by this subtitle, the failure to do so must be fully explained on the travel voucher. Mere inconvenience in the matter of taking receipts will not be considered; and
(3) Receipts must be retained for 6 years and 3 months as prescribed by the National Archives and Records Administration (NARA) under General Records Schedule 6, paragraph number 1 (http://www.archives.gov/records-mgmt/ardor/grs06.html)