I had this exact thing happen and in my state, the judge ruled per diem (which is REIMBURSEMENT for expenses) is allowed to be included in income, BUT only after related expenses have been deducted. Meaning if you get 48 bucks a day, subtract what you spent on tips, meals, etc and whatever is left over is added to income. I usually spend 50-75% , but I told her I would gladly spend 100% in order for her to get 0. She settled on 400 bucks per year.
Illinois BTW