Montana DUI Laws: Penalties, BAC Limit & License (2026)

In Montana the offense is called driving under the influence (DUI), and Montana Code Annotated 61-8-1002 makes it unlawful to drive with a blood or breath alcohol concentration (BAC) of 0.08 percent or more. A first DUI carries 24 hours to 6 months in jail, a $600 to $1,000 fine, and a 6-month license suspension under MCA 61-8-1007.

This guide is part of our DUI Laws by State series.

What counts as a DUI in Montana

Montana's core DUI statute, MCA 61-8-1002, makes it unlawful to drive or be in actual physical control of a vehicle while under the influence of alcohol or drugs, or with a BAC of 0.08 percent or more. The statute creates more than one path to a conviction, so a driver under 0.08 can still be charged if alcohol or drugs impaired the ability to drive safely. Commercial drivers are held to a 0.04 percent limit, and drivers under 21 fall under a 0.02 percent zero-tolerance rule. A BAC of 0.16 percent or more triggers an aggravated DUI with enhanced mandatory penalties. The 0.08 figure is the federal benchmark adopted by every state except Utah, which sets its limit at 0.05 percent, as the National Highway Traffic Safety Administration describes. Montana also treats driving with a BAC of 0.08 or more as its own offense, often called the "per se" DUI, charged alongside or instead of the impairment count.

First-offense DUI penalties in Montana (jail, fines, suspension)

A first DUI under MCA 61-8-1002 is a misdemeanor. According to MCA 61-8-1007, the penalty is imprisonment for not less than 24 consecutive hours and not more than 6 months, and a fine of not less than $600 and not more than $1,000. If a passenger under 16 was in the vehicle, the minimum jumps to 48 consecutive hours and the fine to $1,200 to $2,000. The court typically suspends most of the jail time on the condition that the driver completes a chemical dependency assessment, education, and any recommended treatment. The Montana Department of Justice administers the separate license action, and the Montana DOJ DUI Quick Reference Manual sets out the 6-month suspension and the conditions for a probationary license. Court costs, surcharges, and treatment fees add to the financial total beyond the base fine.

Watch out: The license suspension by the Montana Department of Justice runs on a separate track from the criminal case in court. You can resolve the criminal charge and still face the administrative suspension, and you generally must act quickly to request a hearing or apply for a probationary license.

Ignition interlock requirements in Montana

Montana does not impose an automatic ignition interlock device (IID) on every first offender the way some states do. Instead, the court has discretion to order an IID, and a driver who wants a probationary license to keep driving during the suspension often must install one or enroll in the 24/7 Sobriety Program of monitored testing. The Montana DOJ DUI Quick Reference Manual explains that interlock and 24/7 monitoring are tools the court uses when allowing a restricted driving privilege. For second, third, and felony offenses, interlock and continuous monitoring become far more likely and longer in duration. The device requires a clean breath sample before the engine starts and at random points during a trip, and it records every reading for the court or supervising agency.

License suspension and the administrative process in Montana

Montana runs an administrative license action through the Department of Justice that is separate from the criminal prosecution. For a first DUI, the suspension is 6 months, as the Montana DOJ describes. A driver who needs to keep driving may apply for a probationary license after serving part of the suspension, typically with conditions such as an ignition interlock, SR-22 proof of financial responsibility, and proof of a chemical dependency evaluation. The suspension can stem from either a failed chemical test or a refusal, and the timelines differ for each. To reinstate full driving privileges, a driver generally must serve the suspension, complete the required education or treatment, file any required insurance certificate, and pay reinstatement fees to the Motor Vehicle Division.

Repeat offenses and the Montana look-back period

Montana counts prior DUIs for life, which is one of the harshest look-back rules in the country. There is no washout window, so a DUI from decades ago still counts toward a later offense. A second DUI within the lifetime window carries 7 days to 1 year in jail and a $1,200 to $2,000 fine, and a third carries 30 days to 1 year and a $2,500 to $5,000 fine under MCA 61-8-1007. The felony threshold sits at the fourth offense: under MCA 61-8-1008, a fourth or subsequent DUI is a felony punishable by a fine of $5,000 to $10,000 and a mandatory minimum of 13 months, up to 5 years, in state prison, with even longer terms for further offenses. A DUI that causes injury or death can be charged as a felony such as vehicular assault or negligent vehicular homicide regardless of offense number.

Watch out: Refusing a breath or blood test does not avoid a suspension. A first refusal results in a 6-month suspension, and refusal can be admitted as evidence against you in the criminal case, so it rarely helps.

Refusing a breath or blood test in Montana

Montana's implied consent law means that by driving in the state, you have agreed to submit to a breath, blood, or urine test if lawfully arrested for DUI. A first refusal results in a 6-month license suspension, and a refusal within 5 years of an earlier refusal results in a 1-year suspension, as the Montana DOJ explains. The refusal suspension is administrative and applies whether or not the criminal DUI charge results in a conviction. Officers can also seek a warrant to draw blood after a refusal, particularly in crashes involving injury, and the refusal itself can be used as evidence at trial. Because the refusal suspension can match or exceed the failed-test suspension and adds the warrant risk, refusing seldom benefits the driver.

Can you expunge or seal a DUI in Montana

Montana does not give DUI convictions the same presumption of expungement that other misdemeanors enjoy. Under MCA 46-18-1101, a person who has completed a misdemeanor sentence may petition the district court to expunge the record, but for a DUI the court weighs factors such as the person's age at the time of the offense, the time elapsed, rehabilitation, and the likelihood of reoffending rather than granting it automatically. Expungement is available no more than once in a person's lifetime. A felony DUI generally cannot be expunged under this misdemeanor process. Even when granted, the underlying conviction may still count for look-back purposes, so the practical relief is limited. Many drivers consult a Montana attorney about whether their record qualifies.

What to do after a DUI arrest in Montana

A Montana DUI creates two separate matters at once: a criminal case in court and an administrative license action through the Department of Justice. The deadlines for the license side are short, so a common first step is to address the suspension paperwork and consider applying for a probationary license. The criminal case moves on its own schedule from initial appearance through pretrial and resolution. General information cannot tell you how your case will come out, because the outcome depends on the specific facts, the evidence, and your record. Many people consult a licensed Montana DUI attorney to understand the charge, the deadlines, and the options for both the court case and the license case. Keep copies of the arrest paperwork, any notice of suspension, and any test results in a safe place.