"Taxpayer" means any person identified by a claimant state, under this section, as owing taxes to that claimant state, including the spouse of the taxpayer if the spouse filed a joint return with the taxpayer for the tax year for which tax is owed.
"Claimant state" means any other state of the United States, the City of Philadelphia, Pennsylvania, New York City, New York, or the District of Columbia that extends a like comity for the collection of tax owed to this State.
"Taxes" means any amount of tax imposed on the income of an individual or an estate and paid by the individual or estate under the laws of the claimant state, including any additions to tax for penalties and interest, which is finally due and payable to the claimant state, and with respect to which any administrative or judicial remedies, or both, have been exhausted or have lapsed, and which is legally enforceable under the laws of the claimant state, whether or not there is an outstanding judgment for such sum.
"Refund" means any taxpayer's claim to repayment of an overpayment of gross income tax determined by this State to be owed to the taxpayer by this State, after the overpayment has been applied to any other debt of the taxpayer to this State.
"Tax officer" means a unit or official of a claimant state, or the duly authorized agent of such unit or official, charged with the imposition, assessment or collection of taxes of that state.
N.J.S. § 54A:9-8.4