"Claimant state" means any state or the District of Columbia that requests the withholding of a refund pursuant to this Section and that extends a like comity for the collection of taxes owed to this State.
"Income tax" means any amount of income tax imposed on taxpayers under the laws of the State of Illinois or the claimant state, including additions to tax for penalties and interest.
"Refund" means a refund of overpaid income taxes imposed by the State of Illinois or the claimant state.
"Tax officer" means a unit or official of the claimant state, or the duly authorized agent of that unit or official, charged with the imposition, assessment, or collection of state income taxes.
"Taxpayer" means any individual person identified by a claimant state under this Section as owing taxes to that claimant state, and in the case of a refund arising from the filing of a joint return, the taxpayer's spouse.
35 ILCS 5/911.2