An interlock license is a restricted driver’s license that lets you legally drive any vehicle fitted with an approved ignition interlock device, and only such a vehicle. Every state recognizes it as a valid driving privilege. It carries your photo and license number like any other license, with a restriction code noting the interlock requirement. You can drive to work, school, medical appointments, the grocery store, anywhere you want. The condition is simple and absolute: the car has to have a working device, and you have to use it correctly every time you start the engine.
What the License Actually Grants You
State motor vehicle agencies issue these licenses after a DUI conviction or an alcohol-related administrative suspension. In your driving record it shows up as a restricted privilege, and if an officer pulls you over you present it exactly as you would an unrestricted license.
The restriction itself is not cosmetic. Driving a vehicle without an interlock while your license carries the restriction is a separate offense in most states, usually a misdemeanor. Depending on the state, it can trigger vehicle seizure, arrest, and a restart of your entire interlock period. The license is valid because it’s tied to the device. The two cannot be separated.
How the Device Works
Before the engine will start, you blow into a mouthpiece attached to a unit mounted near your dashboard. It measures your breath alcohol concentration against a preset fail point of 0.02 g/dL, the standard set by the National Highway Traffic Safety Administration’s model specifications.1Federal Register. Model Specifications for Breath Alcohol Ignition Interlock Devices That’s well below the 0.08 legal limit in most states, so a single drink can keep the car from starting.2Centers for Disease Control and Prevention. Increasing Alcohol Ignition Interlock Use
Testing continues after the engine turns over. Within five to seven minutes you’ll be prompted for another sample, and more will follow at random intervals as you drive. These are called rolling retests.1Federal Register. Model Specifications for Breath Alcohol Ignition Interlock Devices The device won’t shut your engine off if you fail or skip one, but it will log the event, sound an alert, and in some cases activate the horn or lights until you pull over and switch off. Once the ignition is off after a failed retest, you’ll need a service visit before the car starts again.
Mouthwash with alcohol, energy drinks, kombucha, certain medications, and even spicy food can produce residual mouth alcohol that registers as a fail. If you get an unexpected reading, most devices let you wait a few minutes and retest. Rinsing with water and avoiding alcohol-based hygiene products before driving prevents most of these problems.
Getting an Interlock License
The path usually begins with a DUI or DWI conviction or an administrative suspension after you refused or failed a chemical test. A court or your state motor vehicle agency will require installation of the device as a condition of getting back on the road. The steps are consistent across most states:
- Choose an approved vendor, schedule installation, and have the vendor submit proof to your state agency.
- File an SR-22 with the state through your insurer. It’s not a separate policy, just a form verifying you carry at least the minimum required liability coverage.
- Complete any required DUI education, substance abuse assessment, or treatment program tied to your case.
- Pay reinstatement fees and clear any other suspensions on your record.
Some states let you apply for the interlock license immediately. Others impose a hard suspension period before you become eligible. The interlock period itself ranges from six months for a first offense in some states to five years for repeat offenders, with most falling between six months and three years.3National Conference of State Legislatures. State Ignition Interlock Laws
What It Costs
Installation runs roughly $70 to $150 as a one-time fee. From there you’ll pay a monthly lease and monitoring charge of about $50 to $120, covering the device rental, data reporting, and regular calibration visits. Over a 12-month period, device costs alone can reach $750 to $1,600.
That’s before the SR-22 insurance premium increase, which varies widely but often doubles or triples your auto insurance cost. Add license reinstatement fees, court costs, and DUI program fees on top. Some states offer financial assistance based on household income, participation in government assistance programs, or employment status. If cost is a barrier, ask your state motor vehicle agency or the court that ordered the interlock about reduced-fee programs.
Where an Interlock License Won’t Help You
Several common assumptions about this license are wrong, and the mistakes are expensive.
Company Vehicles
Roughly 20 states allow an employer exemption that lets you operate a company-owned vehicle without an interlock, for work purposes only. The vehicle must be owned or leased by your employer, not by you, and the employer must provide written consent. Your personal vehicle still needs the device. Using the company vehicle for anything beyond work errands or commuting usually violates the exemption and can cost you the restricted license. Self-employment doesn’t qualify.
Commercial Driving
If you hold a commercial driver’s license, an interlock license does not restore your commercial privileges. Federal law requires a minimum one-year disqualification from operating a commercial motor vehicle after a first alcohol-related offense, even if the offense happened in your personal car.4Office of the Law Revision Counsel. 49 USC 31310 – Disqualifications A second offense triggers a lifetime disqualification, though regulations allow a reduction to no less than 10 years in some cases. The commercial BAC threshold is also lower, 0.04 instead of 0.08. You can drive your personal vehicle with the interlock, but commercial operation is off-limits until the disqualification ends and your CDL is fully reinstated.
Rental Cars
Rentals are effectively unavailable. Major rental companies don’t equip their vehicles with interlock devices and generally won’t rent to anyone whose license carries the restriction. They check driving records through the National Driver Register at the counter, and the restriction shows up. Many companies also refuse to rent to anyone with a DUI on record within the past several years, even after the interlock requirement has ended.
Out-of-State Travel
Your license is valid in your home state. Other states aren’t required to recognize restricted licenses the same way they recognize unrestricted ones. The Interstate Driver License Compact, which most states have joined, shares violation and suspension data between members but doesn’t automatically grant you the right to drive through another state on a restricted license. Some states have specific provisions for honoring out-of-state interlock licenses; others do not. Before any interstate trip, call both your home state motor vehicle agency and the destination state to confirm.
Staying Compliant
The device needs regular service, usually every 30 days, when a certified technician recalibrates it and downloads the stored data log. NHTSA model specifications require a minimum 37-day calibration stability, which is why 30 days has become the standard interval. Missing an appointment counts as a violation.
Every start, every breath test, every rolling retest, and every missed test is recorded with a timestamp. That data goes to whoever monitors your compliance: the motor vehicle agency, a probation officer, or the court. Having someone else blow into the device for you is a criminal offense, with jail time possible for both the driver and the person providing the sample. Tampering with, disconnecting, or bypassing the device is a separate criminal charge in most states.
Violations stack. A single failed test might generate a warning. Repeat failures, missed retests, or a missed calibration can add 180 days or more to your interlock period, trigger a lockout mode that requires a service visit before the car will start, or revoke the restricted privilege entirely and leave you with no license at all.
Getting Back to an Unrestricted License
Restoring full driving privileges requires finishing the interlock period without significant violations. Most states require a clean stretch at the end, typically the last 30 to 120 days with no failed tests, missed retests, or compliance issues. Once that’s done:
- Your vendor submits a final compliance report confirming you met all requirements.
- A certified technician removes the device. Don’t remove it yourself or have it taken out early; both count as violations.
- You apply for an unrestricted license at your state motor vehicle agency and pay reinstatement fees, typically $15 to $125.
Removing the interlock does not end the SR-22 obligation. Most states require you to maintain SR-22 coverage for one to three years after the device comes off, with three years being the most common. Repeat offenses can push that to five. If the policy lapses, your insurer notifies the state and your license can be suspended immediately. Keeping continuous coverage matters long after the device is gone.