What actually happens
An employee who lives in North Dakota and performs work in Montana sits in two tax systems at once. The residence state claims the right to tax all of a resident's income wherever earned; the work state claims the right to tax income sourced within its borders. Montana and North Dakota resolved that overlap by agreement: the work state gives up its claim on commuters' wages entirely.
The certificate is not optional
Reciprocity does not apply automatically because the employee's address is in North Dakota. It applies when the employee gives you a signed MW-4 (Montana Employee's Withholding Allowance and Exemption Certificate (North Dakota reciprocity exemption section; formerly Form MT-R)). Until that form is in your hands you are required to withhold Montana tax, and an auditor will ask to see it. The form stays in your records; it is not filed with the state.
Unemployment insurance goes to one state only
Income tax can be split between states. Unemployment insurance cannot. Under the localization test used by every state, an employee whose services are performed entirely in Montana is covered by Montana for unemployment purposes, and all wages are reported there — regardless of where they live, where you are headquartered, or which state's income tax you withhold. Montana's 2026 taxable wage base is $47,300. The four-factor test in order.
What you have to register for
| Obligation | State | Agency |
|---|---|---|
| Income tax withholding | North Dakota | North Dakota Office of State Tax Commissioner |
| Unemployment insurance | Montana | Montana Department of Labor and Industry, Unemployment Insurance Division |
Frequently asked
Do Montana and North Dakota have a reciprocal tax agreement?
Yes. Montana exempts North Dakota residents from Montana income tax withholding on wages, provided the employee files MW-4 with their employer. Without that form on file the employer must still withhold Montana tax.
Which state's income tax should be withheld?
North Dakota. Under the agreement the wages are taxable only by the state of residence, so you withhold North Dakota tax and stop withholding Montana tax once the certificate is filed.
Which state gets the unemployment insurance wages?
Montana. Unemployment coverage is never split between states for a single job. The localization test assigns the whole job to the state where services are performed, which here is Montana, regardless of residence or where the employer is headquartered.