Montana has several different residency requirements. For the purposes of obtaining a Driver's License, you are considered a resident after 60 consecutive days and must have a Montana license in order to operate a motor vehicle. For a commercial motor vehicle license, the requirement is 30 days. For more information on driver licensing, see Montana Codes Annotated 61-5-103 and the Department of Justice Motor Vehicle Division Driver Licensing page.
For purposes of fishing and hunting licenses, you are considered a resident after 180 consecutive days. After residency has been established, you must live in Montana at least 120 days a year; your principal home must be located in Montana; you must file state income tax returns as a resident (if required to file); vehicles operated in Montana must be licensed and titled as required by law; you can be registered to vote only in Montana; and, you can not claim residency in any other state or country for any purpose. There are different requirements for members of the armed forces. For more information, see Montana Codes Annotated 87-2-102 and the Department of Fish, Wildlife & Parks.
For the purposes of higher education, a student must be domiciled in Montana for one year immediately preceding registration. Attendance as a full-time student is not sufficient to qualify for residence. For more information, see Montana Codes Annotated 20-25-201.