In the absence of an express exemption from State income taxes, no treaty of the Federal Government shall be construed to exempt a corporation from the taxes imposed under Articles IV¹ and VI.² For purposes of determining “taxable income” under Article IV, any corporation not subject to Federal income taxation or Federal reporting requirements pursuant to such a treaty shall be required to file a report with the department showing the taxable income which would have been reported to and ascertained by the Federal Government had it not been exempted by the treaty.