Per Diem is the daily rate an employee or contractor can spend on meals and incidental expenses while on business travel. The per diem rate, sometimes referred to as a flat rate or lump sum, is generally based on the area where the travel is taking place and the type of meal (breakfast, lunch, dinner) that needs to be paid for. Actual Expenses are actual costs incurred, such as airfare, lodging, and car rentals, that must be documented with receipts in order to be reimbursed. Actual Expense reimbursements are usually processed within 30 days of the expense being incurred.