The Internal Revenue Service has issued updated per diem rates that take effect Oct. 1, 2021, which taxpayers can use to substantiate the amount of expenses for lodging, meals, and incidental expenses when traveling away from home. This optional “high-low” per diem rates for lodging expenses and meals and incidental expenses (M&IE) that may be used instead of the General Services Administration’s “actual” per diem rates for travel to locations within the continental U.S.