DUI Laws in Illinois: Penalties, BAC Limits & License Suspension

What Illinois Calls It, and the Numbers You Need First

Illinois calls this offense DUI — Driving Under the Influence, defined at 625 ILCS 5/11-501 of the Illinois Vehicle Code. The standard per se limit is a blood or breath alcohol concentration (BAC) of 0.08% — that number is the same nationwide. Two things are far more urgent than the BAC number itself:

• The clock on your license starts almost immediately. If you failed or refused chemical testing, the Illinois Secretary of State will automatically impose a "statutory summary suspension" of your driving privileges. It takes effect on the 46th day after you were served notice — not right away, but soon.
• You have 90 days to ask a court to stop it. To contest the suspension before it locks in, your lawyer (or you) must file a Petition to Rescind Statutory Summary Suspension in the criminal court handling your case. Courts and defense practitioners describe this 90-day filing window as strict, with few exceptions.

Miss that window, or fail to act before the 46-day mark, and the suspension proceeds automatically — separate from whatever happens later in the criminal case. Everything below explains why this matters and what else is at stake.

Per Se BAC Limits in Illinois

• General adult limit: 0.08%. This is the national per se threshold — Illinois follows it like every other state.
• Commercial driver's license (CDL) limit: 0.04%. This is a federal floor that applies to CDL holders operating a commercial vehicle, adopted into Illinois law as well.
• Under-21 "zero tolerance" limit: 0.00%. Under Illinois's Zero Tolerance Law, a driver under 21 with any measurable trace of alcohol in their system can lose driving privileges, even below 0.08%. According to the Illinois Secretary of State, a first zero-tolerance violation carries a 3-month suspension and a second carries a 12-month suspension; refusing testing as an under-21 driver carries its own separate suspension (6 months for a first violation, 24 months for a second).
• Aggravated / enhanced-penalty threshold: 0.16%. Illinois law (625 ILCS 5/11-501(c-1)) imposes mandatory add-on penalties — minimum fines and mandatory community service that increase with each subsequent offense — once BAC reaches 0.16% or higher, roughly double the general limit.

Because these thresholds and their exact penalty amounts can change, confirm the current text of 625 ILCS 5/11-501 through the Illinois General Assembly's website before relying on a specific dollar figure.

Implied Consent and Refusing a Chemical Test

Driving on Illinois roads means you've already agreed, by law, to submit to a breath, blood, or urine test if a police officer has probable cause to believe you're driving under the influence — this is Illinois's "implied consent" law, 625 ILCS 5/11-501.1. Refusing has two separate consequences:

• An automatic license suspension. For a "first offender" (someone with no qualifying prior DUI disposition in the past 5 years), a first refusal triggers a 12-month statutory summary suspension — twice as long as the 6-month suspension for someone who takes the test and simply fails it. Someone who does not qualify as a first offender faces a longer suspension for refusing (36 months).
• It can be used against you in court. Under 625 ILCS 5/11-501.2, evidence that you refused testing is admissible at trial and prosecutors routinely argue it shows "consciousness of guilt." Refusing does not make the DUI case disappear — it adds a harsher, separate license consequence on top of the underlying charge.

Note: field sobriety tests (walk-and-turn, one-leg stand, etc.) are voluntary in Illinois and declining them does not trigger a license suspension the way declining a chemical test does — but a refusal can still be mentioned at trial.

Administrative License Suspension: Illinois's "Statutory Summary Suspension"

This is the single most time-sensitive part of an Illinois DUI arrest. The Illinois Secretary of State — not a court — administers this suspension, and it happens independently of your criminal case, whether you're ultimately convicted or not.

• Effective date: The suspension automatically begins on the 46th day after you receive the Notice of Summary Suspension (typically handed to you at arrest).
• Deadline to fight it: You (through your attorney) must file a Petition to Rescind Statutory Summary Suspension in court within 90 days of the notice to get a hearing. Once filed, the law generally requires the hearing be held within roughly 30 days, though timing is subject to the court's docket.
• Suspension lengths: 6 months for a first-offender test failure; 12 months for a first-offender refusal; 12 months (one year) for a repeat test failure; and 36 months for a repeat refusal.

Act immediately. Because the suspension takes effect automatically on day 46 regardless of your criminal case's progress, and because the petition deadline is described by Illinois courts as strict with few exceptions, waiting to "see what happens" with the criminal charge can cost you the chance to challenge the suspension at all. Confirm current deadlines and procedure with the Illinois Secretary of State or a local attorney.

First-Offense DUI Penalties in Illinois

A first DUI in Illinois is generally charged as a Class A misdemeanor. Rather than quote precise figures that can shift with amendments, here is the verified general framework — confirm exact current numbers with the Illinois Secretary of State or Illinois courts before relying on them:

• Jail exposure: Class A misdemeanors in Illinois carry a maximum of up to 364 days in county jail, though many first-time, no-injury cases resolve with supervision, probation, or conditional discharge rather than jail time.
• Fines: Class A misdemeanor fines generally run up to $2,500, with mandatory minimum penalties and added community-service hours if your BAC was 0.16% or higher.
• License consequences run on two separate tracks. The statutory summary suspension (6 or 12 months, described above) applies regardless of the criminal outcome. A separate DUI conviction also triggers a revocation of your license by the Secretary of State, which is a distinct process from the summary suspension.
• Ignition interlock (BAIID) is central to driving relief. Illinois's Monitoring Device Driving Permit (MDDP) program allows most first-offense arrestees to keep driving during the summary suspension — but only with a Breath Alcohol Ignition Interlock Device (BAIID) installed. In practice, this makes interlock installation the primary path for a first-time offender who needs to keep driving.

Lookback Period: How Far Back Do Prior DUIs Count?

Illinois treats this differently depending on which system you're looking at:

• For the summary suspension's "first offender" status: a related DUI disposition (conviction, supervision, or a prior summary suspension) from more than 5 years ago generally will not prevent you from being treated as a first offender for the license-suspension length.
• For criminal DUI enhancement (felony triggers): Illinois generally does not use a time-limited lookback. A prior DUI conviction or completed court supervision counts toward enhancement — including the automatic felony bump on a third offense — regardless of how long ago it occurred. In other words, an old DUI from decades earlier can still count as a "prior" for felony purposes even though it may no longer affect your summary-suspension classification.

This dual system is easy to misunderstand, so confirm how your specific prior history is being counted with a local defense attorney.

When a DUI Becomes a Felony ("Aggravated DUI")

Illinois calls a felony-level DUI an "Aggravated DUI," under 625 ILCS 5/11-501(d). Common triggers include:

• A third (or later) DUI — automatically charged as at least a Class 2 felony.
• A DUI that causes a crash resulting in great bodily harm, permanent disability, or death to another person.
• A DUI while transporting a child under 16 where the child is injured, with tiered penalties depending on the severity of the injury and whether it's a repeat offense.
• Driving under the influence without a valid license or insurance, or while your license is already suspended or revoked for a prior DUI.

Aggravated DUI penalty ranges vary substantially by which factor applies and by offense number — confirm the current classification and sentencing range for your specific facts with the Illinois statute or a defense attorney rather than assuming a number.

What to Do After a DUI Arrest in Illinois

1. Read your paperwork the same day. Find the Notice of Summary Suspension and note the date on it — that date starts both the 46-day countdown to suspension and the 90-day countdown to petition for a hearing.
2. Contact a licensed Illinois criminal defense attorney immediately — ideally within days, not weeks. The petition to rescind the summary suspension has to be filed in court, and the process is time-sensitive.
3. Do not wait for your first court date to deal with the license issue. The summary suspension proceeds on its own timeline, separate from your criminal case's schedule.
4. Ask about the Monitoring Device Driving Permit (MDDP) / BAIID program if you need to keep driving during the suspension period.
5. Confirm every deadline and number for yourself. DUI statutes and administrative rules change; verify current figures directly with the Illinois Secretary of State (ilsos.gov) or Illinois courts before making decisions based on this article.
6. Do not attempt to avoid or delay a lawfully requested chemical test through evasive tactics — refusal carries its own automatic license consequence and can be used as evidence against you.

This article is general legal information about Illinois law, not legal advice for your specific situation — consult a licensed Illinois attorney or the Illinois Secretary of State about your case.