We used to do actuals for business trip expenses. It was very obnoxious having to justify every dollar you spent and needing the receipts to back them up. Forget to grab a receipt for a gas station coffee and sandwich and the admin assistant just assumes you were buying cigarettes and a 40oz. Whatever money the company was saving on paying actual expenses, I'm sure they were paying more for approving complicated expense reports. Now, we get per diem and there's no annoying oversight into how you spend your money and what on.