1. The director of revenue, by regulation, may require an employer to timely remit the unpaid amount required to be deducted and withheld by section 143.191 at the end of any quarter-monthly period, only if the employer was required to deduct and withhold six thousand dollars or more in each of at least two months during the prior twelve months.

2. The director may increase the monthly requirement to more than six thousand dollars or otherwise narrow the application of the quarter-monthly remittance system authorized by this section. The director may not require the remittance of withheld taxes more often than monthly unless authorized by this section.

3. A remittance shall be timely if mailed as provided in section 143.851 within three banking days after the end of the quarter-monthly period or if received by the director or deposited in a depository designated by the director within four banking days after the end of the quarter-monthly period.

4. The unpaid amount shall be after a reduction for the compensation provided by section 143.261. The unpaid amount at the end of a quarter-monthly period shall not include unpaid amounts for any prior quarter-monthly period.

5. For purposes of this section, “quarter-monthly period” means:

(1) The first seven days of a calendar month;

(2) The eighth to fifteenth day of a calendar month;

(3) The sixteenth to twenty-second day of a calendar month; and

(4) The portion following the twenty-second day of a calendar month.

6. (1) In the case of an underpayment of any amount required to be paid pursuant to this section, an employer shall be liable for a penalty in lieu of all other penalties, interest or additions to tax imposed by this chapter for violating this section. The penalty shall be five percent of the amount of the underpayment determined under subdivision (2) of this subsection.

(2) The amount of the underpayment shall be the excess of:

(a) Ninety percent of the unpaid amount at the end of a quarter-monthly period; over

(b) The amount, if any, of the timely remittance for the quarter-monthly period.

7. (1) The penalty with respect to any quarter-monthly period shall not be imposed if the employer’s timely remittance for the quarter-monthly period equals or exceeds one-fourth of the average monthly withholding tax liability of the employer for the preceding calendar year. The month of highest liability and the month of lowest liability shall be excluded in computing the average. This subdivision shall apply only to an employer who had a withholding tax liability for at least six months of the previous calendar year.

(2) The penalty shall not be imposed if the employer establishes that the failure to make a timely remittance of at least ninety percent was due to reasonable cause, and not due to willful neglect.

(3) The penalty shall not be imposed against any employer for the first two months the employer is obligated to make quarter-monthly remittance of withholding taxes.

8. Tax amounts remitted under this section shall be treated as payments on the employer’s monthly return required by subsection 2 of section 143.221. Tax amounts remitted under this section shall be deemed to have been paid on the last day prescribed for filing the return. The preceding sentence shall apply in computing compensation under section 143.261, interest, penalties and additions to tax and for purposes of all sections of chapter 143, except this section.

9. The director of revenue may prescribe the use of an electronic funds payment system for the payment of withholding taxes by any employer subject to the requirement of quarter-monthly remittance as provided in this section.