Two mandates, not one
A DUI conviction often produces two separate compliance obligations, and they are independent of each other: having one does not satisfy the other. The SR-22 is an insurance certificate your carrier files with the state to prove you are carrying the liability coverage your state requires. The ignition interlock device is physical hardware bolted into your car that will not let the engine start if it detects alcohol on your breath. One is paperwork held by an insurer. The other is equipment monitored by a device vendor.
They are administered by different parties, they fail in different ways, and they can end on different dates. An SR-22 lapses when a premium goes unpaid. An interlock mandate extends when the device logs a violation. Nothing about a clean interlock record protects you if your policy cancels, and nothing about a paid-up policy protects you if the device reports a failed test. Treating them as one requirement is the most common way drivers lose months off a mandate they were otherwise serving correctly.
What follows is the practical side of running both at once: what the hardware actually does, what it costs, and the four situations that most often turn a compliant driver into a non-compliant one.
What the device actually does
An interlock is a small breathalyzer wired into the ignition circuit. Before the engine will crank, you blow into a handset. If the sample reads above the preset threshold, commonly 0.02% BAC, the car refuses to start and enters a short lockout. That threshold is deliberately far below the 0.08% criminal limit, because the device is enforcing abstinence while driving rather than measuring impairment.
The part drivers underestimate is the rolling retest. At random intervals while you are driving, the device prompts for another sample. This exists to stop someone else blowing into the handset to start the car and then handing over the wheel. A missed rolling retest is logged the same way a failed one is, which matters because you cannot always pull over the moment it prompts.
What it costs to run
The interlock is billed separately from your insurance and does not touch your premium. You lease the hardware from a state-certified vendor, pay to have it installed, and return every few weeks for calibration so the fuel cell stays within tolerance. None of that is optional or negotiable, and the meter runs for the whole mandate.
Recurring lease fee for the hardware and state data reporting.
Mandatory visits every 30-60 days to verify sensor accuracy.
Getting it installed
Installation is sequenced, and the order matters because a restricted or hardship licence usually cannot be issued until the state has proof the device is in the car.
Choose a Certified Provider
Ensure the company is authorized to report data directly to your state’s DMV or court system.
Professional Installation
Technicians must integrate the device with your ignition; tampering with an IID is a felony in most jurisdictions.
Submit Proof of Installation
Once hardware is in, you must provide digital or physical proof to the DMV to activate your hardship license.
How a lockout becomes a longer mandate
The device stores every event and uploads the log at each calibration visit. A failed sample, a missed rolling retest and a power interruption all appear in that log. You will usually not hear about a violation on the day it happens; you hear about it after the download, which is why drivers are often surprised by a notice weeks later.
This is the mechanism that extends mandates. The device is not merely stopping you from driving after a drink, it is producing a monitored record that the state reads.
The battery problem nobody warns you about
An interlock never fully powers down. It has to stay awake to log data and to be ready to prompt the moment you open the door, so it draws a small constant current from the battery. That is a parasitic draw, and on a healthy battery in mild weather it is harmless.
It stops being harmless when the car sits. A vehicle parked for a long weekend, or parked outside in a cold snap, can drop below cranking voltage purely because the device kept drawing while nothing was recharging it. Drivers who use their car daily rarely see this. Drivers who work from home, or who have a second vehicle, see it constantly.
The battery is at 50% capacity; cold weather will likely cause a fail-to-start.
The IID may log a 'Tamper' event; immediate charging is required.
Why a dead battery can look like tampering
Here is the part that turns an inconvenience into a compliance problem. When the device loses power completely it logs a power loss event. Disconnecting the battery to bypass the device produces the same log entry. The device cannot tell the difference, and in many states neither can the review process that reads the report.
So a flat battery can arrive at the DMV looking like an attempt to defeat the interlock. That is why the sequence after a dead battery matters more than the dead battery itself.
Keeping the battery alive
Running an interlock for a multi-year mandate means treating the electrical system as part of your compliance, not as ordinary maintenance.
Use a Smart Trickle Charger
If you don't drive daily, use a 1.5A - 2.0A battery tender to keep voltage in the 12.6V zone.
The 20-Minute Rule
Drive the vehicle for at least 20 consecutive minutes every 48 hours to fully replenish the IID draw.
Upgrade to an AGM Battery
AGM batteries handle deep discharges and parasitic loads significantly better than standard lead-acid types.
Winter is when most violations happen
Fuel cell sensors are temperature sensitive.
The de-icer trap
De-icer fluids are alcohol based.
A winter routine that avoids both problems
The adjustments are small, and they are the difference between a mandate that runs its course and one that gets extended over a cold morning.
Remove the Handset (If Legal)
In permitted states, bring the IID handset inside overnight to keep the sensor at room temperature and eliminate warm-up delays.
Ventilate After De-Icing
Roll down all windows and wait 60 seconds after using windshield de-icer to clear the cabin of ambient alcohol fumes.
Fresh Mouthpiece Check
Always use a dry mouthpiece; moisture from your breath can freeze inside the tube, blocking airflow and causing test failures.
Changing cars in the middle of a mandate
You cannot sell or trade a car with the interlock still in it. The device is leased to you personally and tied to your licence, not to the vehicle, so handing over the keys with the hardware installed can be recorded as an unauthorised transfer or as tampering. Dealerships will not take it either.
What you do instead is a coordinated swap: the vendor removes the device from the old car and installs it in the new one, then reports the new VIN to the state. Book that as a single appointment rather than two, because the gap between removal and reinstallation is the window in which your record shows no compliant vehicle.
Includes labor for removal, re-installation, and technical calibration for the new VIN.
The standard timeframe allowed to update the state with your new vehicle's VIN data.
The SR-22 side of a vehicle change
A vehicle change is also an insurance event, and this is where the two mandates collide. If you hold an owner's policy, the SR-22 filing is tied to the VIN. Removing the old car and adding the new one requires a policy endorsement from your carrier, and the dates have to meet exactly.
A single day where the old vehicle is off the policy and the new one is not yet on it can produce an SR-26 cancellation notice to the state. The SR-26 is what tells the DMV your filing has stopped, and it does not care that the cause was a car purchase rather than a missed payment. Sequence the endorsement before the sale, not after.
Selling the old car cleanly
The order below keeps the paperwork, the hardware and the policy in step, which is the only way the transaction stays invisible to your compliance record.
Secure Authorization
Contact the DMV or court to inform them of the vehicle sale and obtain a digital 'Authorization for Removal'.
Pre-Sale Removal
Schedule the hardware removal at a certified service center before the buyer takes possession of the car.
Execute Insurance Endorsement
Provide the new VIN to your insurance carrier to update your SR-22 filing in real-time.
Verify State Status
Check your state's online driver portal 72 hours later to confirm the new VIN is recorded and compliant.
When the interlock comes off
Removal is not automatic. The mandate ends on a date the state holds, and the device stays in the car until you arrange removal and the vendor reports it. Drivers who assume the vendor tracks the end date for them often pay an extra month of lease.
The SR-22 does not end automatically either, and it usually runs on a different clock. Confirm both end dates with the state rather than with the vendor or the carrier, because only one of those three is the party that decides when you are done.