The IRS states that any meals reimbursed for single day travel are
considered taxable because there are no overnight stays involved.
There is not a business purpose to the Per Diem (for example - an
individual would provide their own lunch normally if there were not
overnights involved, so it’s a benefit to be reimbursed for same day
If you are unsure whether an expense meets the criteria for
reimbursement and/or if it will be considered taxable by the IRS, you
might find this Taxable
Expenses document helpful.