Montana Ignition Interlock — Requirements & Costs
When interlock may be required and practical steps.
When Montana requires an IID §61-8-1010
discretionary; if the court recommends a probationary license, it may restrict driving to vehicles with an ignition interlock device (or order 24/7 sobriety/drug monitoring).
How long the IID must remain installed
no fixed statutory minimum; interlock applies during the probationary license period if ordered (second or subsequent offense: court must order interlock, 24/7 sobriety/drug monitoring, or vehicle forfeiture).
How the device works in practice
Violations and extensions
Common violations that can extend the IID period or trigger additional consequences:
- Failed startup tests (BAC above threshold)
- Failed rolling retests
- Missed calibration appointments
- Tampering with or attempting to circumvent the device
- Operating a vehicle without an IID when one is required
Costs
IID costs are borne by the offender and include:
- Installation fee
- Monthly monitoring/rental fee
- Removal fee
- Calibration fees (may be included in monthly rental or charged separately)
The IID as a path back to driving
While the IID is a restriction, it is also the mechanism that allows many offenders to resume driving sooner than they would under a full suspension. In Montana, restricted driving privileges during the suspension period are limited. Complying fully with IID requirements — no violations, on-time calibration — is the fastest path to full reinstatement.
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Frequently Asked Questions
General answers to common questions. Specific outcomes depend on your facts and timing.
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