SEC. 10. WITHHOLDING AND

PAYMENT OF EMPLOYMENT TAXES.

.01 The portion of a mileage allowance (other than a FAVR al

lowance), if any, that relates to the miles of business travel substantiated and that exceeds the amount deemed substantiated for those miles under section 9.01(1) is subject to withholding and payment of employment taxes. See § 1.62–2(h)(2)(i)(B).

(1) In the case of a mileage allowance paid as a reimbursement, the excess described in this section 10.01 is subject to withholding and payment of employment taxes in the payroll period in which the payor reimburses the expenses for the business miles substantiated. See § 1.62–2(h)(2)(i)(B)( 2 ),

(2) In the case of a mileage allowance paid as an advance, the excess described in this section 10.01 is subject to withholding and payment of employment taxes no later than the first payroll period following the payroll period in which the business miles with respect to which the advance was paid are substantiated. See § 1.62–2(h)(2)(i)(B)( 3 ). If some or all of the business miles with respect to which the advance was paid are not substantiated within a reasonable period of time and the employee does not return the portion of the allowance that relates to those miles within a reasonable period of time, the portion of the allowance that relates to those miles is subject to withholding and payment of employment taxes no later than the first payroll period following the end of the reasonable period. See § 1.62–2(h)(2)(i)(A).

(3) In the case of a mileage allowance that is not computed on the basis of a fixed amount per mile of travel (e.g., a mileage allowance that combines periodic fixed and variable rate payments, but that does not satisfy the requirements of section 8), the payor must compute the amount, if any, that exceeds the amount deemed substantiated under section 9.01(1) periodically (no less frequently than quarterly) by comparing the total mileage allowance paid for the period to the applicable standard mileage rate in section 5.01 or 6.01 multiplied by the number of business smiles substantiated by the employee for the period. Any excess is subject to withholding and payment of employment taxes no later than the first payroll period following the payroll period in which the excess is computed. See § 1.62– 2(h)(2)(i)(B)( 4 ).

(4) For example, assume an employer pays its employees a mileage allowance at a rate of 35 cents per mile (when the business standard mileage rate is 31 cents per mile). The employer does not require the return of the portion of the allowance (4 cents) that exceeds the business standard mileage rate for the business miles substantiated. In June, the employer advances an employee $175 for 500 miles to be traveled during the month. In July, the employee substantiates to the employer 400 business miles traveled in June and returns $35 to the employer for the 100 business miles not traveled. The amount deemed substantiated for the 400 miles traveled is $124 and the employee is not required to return the remaining $16. No later than the first payroll period following the payroll period in which the 400 business miles traveled are substantiated, the employer must withhold and pay employment taxes on $16.

.02 The portion of a FAVR allowance, if any, that exceeds the amount deemed substantiated for those miles under section 9.01(2) is subject to withholding and payment of employment taxes. See § 1.62–2(h)(2)(i)(B).

(1) Any periodic variable rate payment that relates to miles in excess of the business miles substantiated by the employee and that the employee fails to return within a reasonable period, or any portion of a periodic fixed payment that relates to a period during which the employee is treated as not covered by the FAVR allowance and that the employee fails to return within a reasonable period, is subject to withholding and payment of employment taxes no later than the first payroll period following the end of the reasonable period. See § 1.62–2(h)(2)(i)(A).

(2) Any optional high mileage payment is subject to withholding and payment of employment taxes when paid.