The commissioner shall determine the part of the net income of a financial institution derived from business carried on within the commonwealth as follows:
If, after such application by the financial institution, or after the commissioner's own review, the commissioner determines that the provisions of subsections (a) to (f), inclusive, are not reasonably adapted to approximate the financial institution's net income derived from business carried on within the commonwealth, the commissioner shall by reasonable methods determine the amount of net income derived from business activity carried on within the commonwealth. The amount thus determined shall be the net income taxable under section two and the foregoing determination shall be in lieu of the determination required by subsections (a) to (f), inclusive. If an alternative method is used by the commissioner hereunder, the commissioner, in his discretion, with respect to the two next succeeding taxable years, may require similar information from such financial institution if it shall appear that the provisions of subsections (a) to (f), inclusive, are not reasonably adapted to approximate for the applicable year the financial institution's net income derived from business carried on within this commonwealth and may again by reasonable methods determine such income.
Mass. Gen. Laws ch. 63, § 2A