The reimbursement of employee business expenses is not taxable to the employee if the employer has a:

a. Plan that requires the employee to substantiate the expenses but does not require the return of any excess reimbursement.

b. Plan that requires the employee to substantiate the expenses and return any excess reimbursement.

c. Plan that does not require substantiation but does require the return of any excess reimbursement.

d. Plan that requires all employees to report all reimbursements as income.