State service guide

Montana DUI laws: 0.08 adult standard, 0.02 under-21 rule, and suspension-first fallout for refusal and repeat cases

Montana's DUI rules split quickly between criminal penalties and driver-license sanctions. The practical numbers are 0.08 for most adult alcohol cases, 0.02 for drivers under 21, and 0.04 for commercial drivers operating a commercial vehicle. On the license side, Montana MVD currently lists a 6-month suspension for a first DUI or 0.08-plus conviction, 6 months for a first refusal, and 90 days for a first under-21 0.02-plus conviction. On the criminal side, first-offense penalties can reach six months in jail and a $600 to $1,000 fine, and a fourth or subsequent DUI is a felony.

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Adult alcohol threshold 0.08 BAC for most adult alcohol cases
Under-21 threshold 0.02 BAC
First license suspension 6 months for a first DUI or 0.08-plus conviction, and 6 months for a first refusal
Commercial threshold 0.04 BAC while operating a commercial motor vehicle

Overview

What this page helps you verify

A useful Montana DUI page should not collapse everything into one adult 0.08 chart. Montana's current official materials separate ordinary DUI convictions, under-21 alcohol cases, commercial-driver alcohol cases, refusal suspensions, aggravated DUI treatment, and repeat-offense escalation. The better user-facing explanation is procedural first: identify which threshold applies, then separate the MVD suspension table from the court penalties, and then check whether ignition interlock, a probationary restriction, treatment, or a 24/7 sobriety condition will control the return-to-driving path.

Last reviewed: 2026-05-18. This page was manually upgraded against service-specific official sources, but requirements can still change quickly.

Usually needed

Documents and information to prepare

  • The DUI arrest paperwork, including any notice of suspension, test results, or refusal documents
  • Court paperwork showing the charged subsection, offense date, and whether the state is treating the case as a repeat or aggravated DUI
  • Any MVD paperwork tied to driver-license seizure, suspension status, or probationary licensing restrictions
  • Chemical dependency assessment, education-course, treatment, or monitoring records required for reinstatement or sentencing compliance
  • Ignition interlock installation or compliance records if the court or department restricts driving to an interlock-equipped vehicle

Typical flow

What the process often looks like

  1. Identify first whether the case is a standard adult DUI, an under-21 0.02-plus case, a commercial-driver alcohol case, a refusal case, or an aggravated DUI case, because Montana uses different thresholds and penalties across those branches.
  2. Treat the MVD suspension separately from the criminal DUI case, because the state publishes a distinct license-suspension chart for convictions and refusals.
  3. Check whether the record now triggers ignition interlock, a probationary-license restriction, treatment, chemical dependency monitoring, or a 24/7 sobriety condition instead of assuming the issue ends when the suspension period runs.
  4. Before expecting full restoration of driving privileges, clear the MVD status and complete the education, treatment, and other court-ordered conditions tied to the offense level.

Thresholds

Montana DUI law is not just one 0.08 adult rule

This is the first correction a state-specific page should make.

  • Montana's current driver manual says you can be arrested for driving with a blood alcohol concentration of 0.08 or more or while driving under the influence.
  • The same official materials use 0.02 for drivers under 21 years of age.
  • Montana MVD separately lists a 0.04 alcohol threshold for a commercial driver operating a commercial motor vehicle.

License consequences

Montana's MVD suspension chart starts with six months and then escalates quickly for refusals, repeat cases, and commercial drivers

This is the most practical part of the page for people trying to understand whether they can still drive.

  • MVD currently lists a 6-month suspension for a first conviction for DUI or operating with a BAC of 0.08 or greater, and a 1-year suspension for a second or subsequent conviction within 10 years.
  • For refusal to submit to alcohol testing, MVD lists a 6-month suspension for a first refusal and a 1-year suspension for a second or subsequent refusal.
  • For a person under 21 with a BAC of 0.02 or more, MVD lists a 90-day suspension for a first conviction, 6 months for a second, and 1 year for a third.
  • For a commercial driver operating a commercial motor vehicle with a BAC of 0.04 or more, MVD lists a 1-year suspension on the first violation, 3 years if hazardous materials requiring a placard were involved, and life on a second or subsequent violation, subject to reconsideration after 10 years.

Criminal penalties

Court penalties in Montana depend on which DUI subsection applies and how many prior convictions are on the record

Montana's current DOJ quick-reference chart is more nuanced than a generic first-offense summary.

  • The DOJ driver manual says a first alcohol-related DUI conviction can bring up to 6 months in jail and a fine of up to $1,000, plus a 6-month suspension.
  • The current DOJ DUI quick-reference chart shows that first-offense penalties under section 61-8-1002 can start at $600 to $1,000, with some first-offense variants carrying no minimum jail term and others carrying a 24-consecutive-hour minimum.
  • That same chart shows second-offense fines of $1,200 to $2,000 with a 5-day or 7-day minimum jail term depending on the DUI subsection, and a third offense at $2,500 to $5,000 with a 30-day minimum jail term.
  • Montana's official driving-safety page says a fourth or subsequent DUI is a felony.

Aggravation and restoration

Montana layers aggravated-DUI treatment, child-passenger enhancements, treatment, and interlock on top of the ordinary DUI framework

This is where the state-specific details go beyond a basic adult first-offense chart.

  • Montana's current DOJ DUI quick-reference manual describes aggravated DUI as a penalty enhancement that applies in situations including 0.16 BAC, driving while under an ignition-interlock order, driving while suspended or revoked from a prior DUI-related matter, or refusing a breath sample after a prior implied-consent suspension.
  • The same quick-reference chart shows higher mandatory jail terms and fines when a passenger under 16 was in the vehicle.
  • MVD says a driver convicted of DUI or with a BAC of 0.08 or more may be restricted to operating a vehicle equipped with an ignition interlock device.
  • MVD also says drivers charged or convicted of a second or subsequent DUI offense can be ordered into the 24/7 Sobriety Program, and the DOJ chart ties repeat cases to chemical dependency assessment, education, treatment, and monitoring requirements.

Accuracy notes

Where people get tripped up

  • Montana DUI content should not be written as one flat adult 0.08 page. The official state sources separate adult, under-21, commercial, refusal, and aggravated-DUI paths.
  • The MVD suspension chart and the criminal sentencing chart do different jobs. Montana pages are strongest when they keep those two tracks separate.
  • A generic first-offense summary can overstate the jail minimum. Montana's current DOJ chart distinguishes between subsection-level first offenses, including versions with no minimum jail term and versions with a 24-hour minimum.
  • Montana restoration should be framed around treatment, monitoring, probationary restrictions, and possible ignition interlock, not just around waiting out the calendar.

FAQ

Common questions

  • What BAC counts as DUI in Montana?

    For most adult alcohol cases, Montana uses 0.08. The official state materials use 0.02 for drivers under 21 and 0.04 for a commercial driver operating a commercial motor vehicle.

  • What happens to my Montana license if I refuse the alcohol test?

    Montana MVD says a first refusal to submit to alcohol testing brings a 6-month suspension, and a second or subsequent refusal brings a 1-year suspension.

  • Is every first Montana DUI treated the same in court?

    No. Montana's current DOJ quick-reference chart shows different minimum jail terms depending on the DUI subsection. Some first-offense variants carry no minimum jail term, while others carry a 24-consecutive-hour minimum.

  • Is a fourth Montana DUI a felony?

    Yes. Montana's official driving-safety page states that a fourth or subsequent DUI is a felony.

  • When does ignition interlock matter in Montana DUI cases?

    Montana MVD says a driver convicted of DUI or with a BAC of 0.08 or more may be restricted to an ignition-interlock-equipped vehicle, and the DOJ quick-reference manual treats an existing interlock order as one of the aggravated-DUI triggers.

Sources

Official references used for this page

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