The following credits shall be allowed against the tax imposed by this chapter:

1. (a) A credit shall be allowed against taxes imposed by this chapter to a resident for taxes due any other state, territory or possession of the United States, or the Dominion of Canada or any of its provinces on account of any item of Massachusetts gross income subject to the following restrictions and limitations:
2. (i) the amount of such taxes due on such income shall exclude interest and penalties;

3. (ii) the amount of such taxes due shall be reduced by any federal credit therefor allowable on the resident's federal income tax return; and (iii) the amount of the credit allowable shall be the lesser of such taxes as reduced by (i) and (ii), or the amount of tax imposed by this chapter multiplied by a fraction the numerator of which is such item of Massachusetts Part A, Part B or Part C income and the denominator of which is the total Massachusetts Part A, Part B or Part C income, as the case may be. The credit hereunder shall be allowed to estates of residents and to trustees or other fiduciaries described in subsection (c) of section ten.

   In the case of dividends received out of tax-free earnings and profits of a corporate trust previously subject to tax under this chapter, shareholders of the corporate trust shall be entitled to a credit for income taxes paid to other jurisdictions on those earnings and profits, either by the corporate trust or by the shareholders, as otherwise calculated under this subsection.

   [There is no subsection (b) or (c).]