What proof is needed for per diem?

For per diem under JTR Joint Travel Regulations and Federal Travel Regulation, proof needed is generally lodging receipt for lodging portion, while meals and incidental expenses M&IE are paid as flat rate without receipts. Under JTR, per diem consists of lodging reimbursement up to authorized rate plus M&IE flat rate based on location. To claim per diem, you need authorized travel orders, proof of travel such as itinerary, and lodging receipt. Lodging receipt must be itemized showing daily room rate, taxes, fees, dates, and proof of payment, and is always required regardless of amount, even if lodging is under 75 dollars. For M&IE, you receive flat per diem rate based on TDY location, no receipts required for meals, but you must report if meals were provided free by government or conference to reduce M&IE. If claiming actual expense for lodging above per diem due to high cost area, you need justification and approval plus receipts. For meals, if you claim actual expense instead of per diem, you need receipts and approval. For incidental expenses like tips, no receipt needed under 75 dollars. In Defense Travel System DTS, you upload lodging receipt and certify travel. So proof needed for per diem is lodging receipt itemized, travel orders, and if required, justification for actual expense, while M&IE requires no receipt but is based on location per diem table published by GSA and DTMO.