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 up to 6 months in jail, a $600 to $1,000 fine, and a 6-month license suspension under MCA 61-8-1007. The 24-hour mandatory minimum attaches only to the impairment count, not to the 0.08 per se count.

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, and under MCA 61-8-1001 three other triggers do the same: being under a court or department order to use an approved ignition interlock device, driving while your license is suspended, canceled, or revoked because of a prior DUI violation, or refusing a breath sample and having your license suspended under implied consent. Any one of them is enough, so a repeat or refusing driver can face aggravated exposure well below 0.16. 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 depends on which count the driver is convicted of. For the impairment count under MCA 61-8-1002(1)(a), subsection (1)(a)(i) sets imprisonment of not less than 24 consecutive hours and not more than 6 months, and a fine of $600 to $1,000. For the 0.08 per se count and the commercial, THC, and drug-threshold counts under MCA 61-8-1002(1)(b), (1)(c), (1)(d), and (1)(f), subsection (2)(a)(i) sets imprisonment of not more than 6 months and the same $600 to $1,000 fine, with no mandatory minimum jail term at all. If a passenger under 16 was in the vehicle, the impairment-count minimum rises 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 whose suspension follows a failed chemical test may apply for a probationary license, typically with conditions such as an ignition interlock, SR-22 proof of financial responsibility, and proof of a chemical dependency evaluation. A refusal suspension is different in kind, not merely on a different timeline: under MCA 61-8-1032, the department may not issue a probationary license during an implied consent suspension, and the statute sets 6 months for a first refusal and 1 year for a second or subsequent refusal within 5 years, each with no provision for a restricted probationary license. 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

MCA 61-8-1011 sets the counting rule, and it is not a lifetime rule for every offense. A prior conviction counts if less than 10 years elapsed between the commission of the present offense and that conviction, unless the present offense is the third or subsequent one, in which case all prior convictions must be used for sentencing. So a 12-year-old prior does not turn the present case into a second offense, but once a driver reaches a third offense the age of the priors stops mattering. A second DUI carries 7 days to 1 year in jail on the impairment count, or 5 days to 1 year on the per se and drug counts, plus 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 the court must impose either 13 months to 2 years in a correctional placement followed by a consecutive 5-year state prison term that is suspended unless probation conditions are violated, or up to 5 years in a treatment court program, with harsher mandatory prison 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 with no probationary license available during it, 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. MCA 61-8-1032 allows no restricted probationary license during either one, so a refusal suspension means no lawful driving at all until it runs out. A refusal that results in a suspension can also make the underlying DUI an aggravated DUI under MCA 61-8-1001. 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 the Misdemeanor Expungement Clarification Act, a person who has completed a misdemeanor sentence may petition the district court to expunge the record, but MCA 46-18-1108 excludes DUI from the presumption of expungement and requires the court to weigh factors such as the person's age at the time of the offense, the time elapsed, rehabilitation, and the likelihood of reoffending before granting it. Expungement is available no more than once in a person's lifetime under MCA 46-18-1104. 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.

More Montana Laws

• Montana Expungement Laws
• Montana Warrant Search