Business travelers who incur expenses while traveling away from home have new per-diem rates to use in substantiating certain of those expenses. The new rates are in effect from Oct. 1, 2018, to Sept. 30, 2019. The IRS provided the 2018–2019 special per-diem rates, including the transportation industry meal and incidental expenses rates, the rate for the incidental-expenses-only deduction, and the rates and ...