Reciprocity agreement

Around thirty such agreements exist in the United States, concentrated in the mid-Atlantic and the industrial Midwest where daily cross-border commuting is common. They are administrative arrangements between revenue departments rather than federal law, and either side can end one: Minnesota and Wisconsin held an agreement until 2010 and have not revived it.

The mechanism is withholding, not liability. Without an agreement, both states are entitled to tax the same wages and the overlap is unwound afterwards through a credit. With one, the work state simply never withholds, so the money is never in the wrong place to begin with. That makes an agreement worth more than the credit it replaces, because a credit is capped and a non-payment is not.

The certificate is the part that goes wrong. It belongs to the state where the work is performed, it is handed to the employer rather than mailed to a revenue department, it is not applied automatically, and it is not retroactive. An employee who files it in June does not recover what was withheld in January by filing it — they recover it by filing a nonresident return for that year.