SECTION 1. Subsection (c) of section 3 of chapter 63B of the General Laws, as so appearing, is hereby amended by striking out the first and second sentences and inserting in place thereof the following 3 sentences:- 

“For purposes of this chapter, there shall be 4 required installments for each taxable year, except as otherwise provided by this chapter. The first installment shall be paid on or before the fifteenth day of the third month of the taxable year; the second installment shall be paid on or before the fifteenth day of the sixth month of the taxable year; the third installment shall be paid on or before the fifteenth day of the ninth month of the taxable year; and the fourth installment shall be paid on or before the fifteenth day of twelfth month of the taxable year. The amount of each installment shall be 25 per cent of the required annual payment.”

SECTION 2. Section 4A of chapter 63B of the General Laws, as so appearing, is hereby amended by striking out the first and second sentences and inserting in place thereof the following 2 sentence:-

“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 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-five 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, seventy-five 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-five percent of the estimated tax.”