Section 4B. A corporation that has less than ten employees and is in its first full taxable year of doing business shall not be subject to the schedules set forth in subsection (c) of section three and section four A. For purposes of such corporation there shall be four required installments for each taxable year, except as otherwise provided by this chapter. The first such installment shall be paid on or before the fifteenth day of the third month of the taxable year and shall be equal to thirty percent of the required annual payment; the second such installment shall be paid on or before the fifteenth day of the sixth month of the taxable year and shall be equal to twenty-five percent of the required annual payment; the third such installment shall be paid on or before the fifteenth day of the ninth month of the taxable year and shall be equal to twenty-five percent of the required annual payment; and the fourth such installment shall be paid on or before the fifteenth day of the twelfth month of the taxable year and shall be equal to the remaining twenty percent of the required annual payment.

If the first required installment of estimated tax is paid after the fifteenth day of the third month of the taxable year and is required by section four to be paid on or before the fifteenth day of the sixth month of the taxable year, fifty-five percent of the estimated tax shall be paid; the second required installment shall be paid on or before the fifteenth day of the ninth month of the taxable year and shall be equal to twenty-five percent of the estimated tax; and the last installment shall be paid on or before the fifteenth day of the twelfth month of the taxable year and shall be equal to the remaining twenty percent of the estimated tax.

If the first required installment of estimated tax is paid after the fifteenth day of the sixth month of the taxable year and is required by section four to be paid on or before the fifteenth day of the ninth month of the taxable year, eighty percent of the estimated tax shall be paid; and the last installment shall be paid on or before the fifteenth day of the twelfth month of the taxable year and shall be equal to the remaining twenty percent of the estimated tax.

If the first required installment of estimated tax is paid after the fifteenth day of the ninth month of the taxable year and is required by section four to be paid on or before the fifteenth day of the twelfth month of the taxable year, the estimated tax shall be paid in full on or before the fifteenth day of the twelfth month of the taxable year.

Such corporations shall be subject to all other provisions of this chapter.