The IRS permits the use of per diem rates for meals and incidental expenses and a separate rate for lodging for the deduction of travel expenses. The amount of the rates depends upon the location that is traveled to. As an example, travel to NYC will be deductible at a higher rate than to a more rural area like Vermont.
It is important to remember is that only employees can use these rates. If an employee is an owner of a business or related to the owner, they cannot use the per diem rates. If you are self-employed, you cannot use them to substantiate travel expenses, you must use actual costs.