Per diem payments are not part of the employee’s wages if the payment is equal to or less than the federal per diem rate and the employer receives an expense report from the employee.
https://www.irs.gov/pub/irs-regs/perdiemfaq%26a.prn.pdf
If the individual is not an employee, than a Form 1099NEC will be issued to the individual for the amounts paid in the year.
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