Income taxes imposed by other states.

Before the allowance of any credit under § 111.1 (relating to tax withheld), a resident taxpayer will be allowed a credit against tax otherwise due under this chapter for amounts paid to another state for any income tax, wage tax, or other tax on or measured by gross or net earned or unearned income imposed upon income which is also subject to tax under this article. For example, if a resident taxpayer earns wages in Delaware and pays an income tax thereon to the State of Delaware, he shall be entitled to a credit against the Commonwealth income tax liability imposed upon wages.