(1) A resident individual or resident estate or trust is allowed a credit against the tax due under this part for the amount of an income tax imposed on the resident individual or resident estate or trust for the tax year by another state of the United States, a political subdivision of another state of the United States, the District of Columbia, or a Canadian province, on income derived from sources outside this state that is also subject to tax under this part or the amount determined under subsection (3), whichever is less. For purposes of the Canadian provincial credit, the credit is allowed for only that portion of the provincial tax not claimed as a credit for federal income tax purposes. It is presumed that the Canadian federal income tax is claimed first. The provincial tax claimed as a carryover deduction as provided in the internal revenue code is not allowed as a credit under this section.

    (2) The Canadian provincial credit shall be allowed for the 1978 tax year and for each tax year after 1978.

    (3) The credit under this section shall not exceed an amount determined by dividing income that is subject to taxation both in this state and in another jurisdiction by taxable income and then multiplying that result by the taxpayer’s tax liability before any credits are deducted.