i can't think of how this is appropriate for anyone. i would assume you get per diem (and that doesn't matter, really...it just matters that you're eligible for per diem). because the deduction you'd already be taking off of the gsa numbers for per diem allowances include tips. there's no legitimate reason to deduct tips separately unless you're just not taking advantage of the real money to be had in deducting the difference between your per diem and the gsa numbers.