Section 620-A - Credit against separate tax(a) General. A resident shall be allowed a credit against the separate tax otherwise due under section six hundred three for any income tax imposed for the taxable year by another state of the United States, a political subdivision of such state, the District of Columbia or a province of Canada, upon the ordinary income portion (or part thereof) of a lump sum distribution both derived therefrom and subject to tax under such section. Where such ordinary income portion (or part thereof) of a lump sum distribution is not subject to separate income taxation by such other state or its political subdivision or the District of Columbia or a province of Canada, but is included as income under an income tax imposed by such jurisdiction, the portion of the tax on such income which constitutes the income tax imposed on such ordinary income portion (or part thereof) of a lump sum distribution shall be an amount bearing the same ratio to the entire tax paid to such other jurisdiction as the amount of the ordinary income portion (or part thereof) of a lump sum distribution included in the income subject to such tax bears to all income subject to such tax.(b) Limitations. (1) The credit under this section shall not exceed the percentage of the tax otherwise due under section six hundred three determined by dividing the portion of the taxpayer's ordinary income portion of a lump sum distribution taxable both under section six hundred three and by such other jurisdiction by the total amount of the taxpayer's ordinary income portion of a lump sum distribution taxable under section six hundred three.(2) The credit under this section shall not reduce the tax otherwise due under section six hundred three to an amount less than would have been due if the portion of the ordinary income portion of a lump sum distribution taxable both under section six hundred three and by such other jurisdiction were excluded from the computation of the separate tax imposed under section six hundred three.(3) In the case of a taxpayer who elects to claim the foreign tax credit for federal income tax purposes, the credit under this section for income tax imposed by a province of Canada shall be allowed for that portion of the provincial tax not claimed for federal purposes for the taxable year or a preceding taxable year, provided however, to the extent the provincial tax is claimed for federal purposes for a succeeding taxable year, the credit under this section must be added back in such succeeding taxable year. The provincial tax shall be deemed to be claimed last for federal income tax purposes and for purposes of this subsection.