Section 6
SEC. 6. Subsections (b) and (d) of section forty-six of Commonwealth Act Numbered Four hundred sixty-six, as amended, are hereby further amended to read as follows: "(b) When to file.—The return shall be filed on or before the fifteenth day of April of each year for the preceding calendar year, or if the corporation has designated a fiscal year, on or before the fifteenth of the fourth month following the close of such fiscal year. "(d) Fiscal year of corporations.—Every corporation subject to tax, including duly registered general copartnerships, may designate the last day of any month in the year as the day of the closing of its fiscal year, and shall be entitled to have the tax payable by it computed upon the basis of the net income ascertained as herein provided for the year ending on the day so designated in the year Receding the date of assessment instead of upon the basis of the net income for the calendar year preceding the date of assessment; and it shall give notice of the day it has thus designated as the closing of its fiscal year to the Commissioner of Internal Revenue at any time not less than thirty days prior to the fifteenth day of April of the year in which its return would be filed if made upon the basis of the calendar year."