The Term “Per Diem” is used by U. S. General Services Administration, A U S counterpart of our CPWD, DOPT & Deptt of expenditure. They provide for different rules & norms. What I understand by “Per Diem” is equivalent to earlier Daily Allowance. In USA Government employee have to submit itemized list of expenses incurred during the tour. But they have submit the actual receipts if total expenses exceeds $75/-. Kindly refer website ---- Home > About GSA > Reference > Regulations > Federal Travel Regulation > Table of Contents. These FTA rules elaborates all regulations regarding US TA /DA