Rev. Proc. 2010-39, 2010-42 I.R.B. 1

(IRS publishes updates rules for determining amount of an employee's ordinary and necessary business expenses for lodging, meals and incidental expenses incurred during travel that will be deemed substantiated under Treas. Reg. Sec. 1.274-5; high per diem allowance is $233 and low rate is $160, effective for travel after Sept. 30, 2010).