Hi and welcome to our site!Taxpayers have a choice - either deduct actual travel expenses OR use the standard Per Diem rate. When the standard Per Diem rate is used - it doesn't matter what were actual expenses - and there is no need to keep all receipts. The purpose of using the standard Per Diem rate is to simplify record keeping and audit procedure.
Generally, you can use the “standard meal allowance” method as an alternative to the actual cost method. It allows you to use a set amount for your daily meals and incidental expenses (M&IE), instead of keeping records of your actual costs.If you use the standard meal allowance, you still must keep records to prove the time, place, and business purpose of your travel. However - receipts to proof your mean expenses are not required. So if there are some receipts - that is OK to proof the time and place of your travel. But as it was mentioned above - there is no need to proof amounts of expenses.But generally - a schedule of the shows indicating the dates might be used as supporting documents.
Also - the taxpayer may maintain his/her own travel log - and that will be used as supporting document.