Understanding the underinsured motorist setoff in Illinois is one of the most important — and most misunderstood — aspects of any UIM claim. Many policyholders assume that their UIM coverage limit is the amount they can actually collect. In practice, it is not. Illinois law requires that the at-fault driver’s liability payment be subtracted from the UIM limit before you receive anything from your own insurer. The result is often far less than the policy number on the declarations page suggests.
This article provides general legal information; consult with a licensed Illinois attorney for advice specific to your situation.
What Is an Underinsured Motorist Setoff in Illinois?
Illinois UIM coverage is governed by 215 ILCS 5/143a-2. Under that statute, underinsured motorist coverage is designed to compensate you when the at-fault driver’s liability limits are insufficient to cover your actual damages. However, the statute — and the standard Illinois auto policy — operates on a “difference in limits” or “setoff” basis rather than a “stacking” basis. This means your insurer calculates its maximum payment by subtracting what the at-fault driver’s insurer paid from your own UIM limit, not by simply adding the two amounts together.
Illinois Supreme Court decisions interpreting 215 ILCS 5/143a-2 have consistently upheld this setoff structure. The practical effect is that your UIM coverage only activates meaningfully when your damages exceed the at-fault driver’s policy limits, and even then, the net amount your UIM insurer pays is reduced by whatever the at-fault insurer already paid.
A Worked Hypothetical: How the Underinsured Motorist Setoff Illinois Calculation Works
The following example uses hypothetical numbers for illustration only. These figures do not represent any specific case outcome or guarantee of recovery.
Hypothetical facts:
- Your total verifiable damages (medical bills, lost wages, pain and suffering): $120,000
- At-fault driver’s bodily injury liability limit (per person): $30,000 (Illinois minimum under 625 ILCS 5/7-203 as amended by P.A. 103-0514)
- Amount paid by the at-fault driver’s insurer: $30,000
- Your own UIM policy limit (per person): $100,000
Step 1 — Does the other driver qualify as “underinsured”?
Yes. The at-fault driver’s per-person limit ($30,000) is less than your UIM limit ($100,000). The at-fault driver is underinsured by definition under 215 ILCS 5/143a-2.
Step 2 — Apply the setoff.
Maximum your UIM insurer can pay = UIM limit minus the at-fault driver’s payment
$100,000 (UIM limit) − $30,000 (at-fault payment) = $70,000 maximum UIM payment
Step 3 — Total recovery.
$30,000 (at-fault insurer) + $70,000 (UIM insurer, net of setoff) = $100,000 total
The gap. Even though your damages are $120,000 and you hold a $100,000 UIM policy, your total insurance recovery is capped at $100,000 — a $20,000 shortfall. The UIM policy did not add $100,000 on top of the liability payment; it defined the ceiling of combined recovery.
Why the New Illinois Minimum Limits Matter for UIM Claims
Public Act 103-0514 raised Illinois’s mandatory minimum bodily injury liability limits from 25/50/20 to 30/60/25, effective January 1, 2025, under 625 ILCS 5/7-203. This change has a direct effect on UIM setoff math. As the at-fault driver’s minimum required limit increases from $25,000 to $30,000 per person, the amount subtracted from your UIM limit in a setoff also increases — meaning your UIM insurer’s net payment decreases by a corresponding $5,000 in a limits-minimum scenario. If you purchased your UIM coverage before the minimum change, it is worth reviewing your declarations page to ensure your UIM limit still provides the gap coverage you intended.
For additional background on handling insurance coverage after a crash, see our uninsured and underinsured driver claims overview.
Common Misconceptions About UIM Coverage in Illinois
Several myths persist about how UIM coverage works. The most common is that a $100,000 UIM policy means you receive $100,000 from your insurer in addition to whatever the at-fault driver pays. As the example above shows, that is not how Illinois policies are structured under 215 ILCS 5/143a-2. Other misconceptions include:
- Myth: UIM always pays the difference between your damages and what you received. Fact: UIM pays the difference between the at-fault driver’s limits and your UIM limit — not the difference between your actual damages and the payment received. If your damages exceed your UIM limit, you still face a shortfall.
- Myth: You must litigate the at-fault driver before filing a UIM claim. Fact: You generally must exhaust the at-fault driver’s liability limits first and obtain your insurer’s consent before settling with the at-fault insurer, but a full trial is not required.
- Myth: Umbrella policies are subject to UIM setoff rules the same way primary policies are. Fact: Umbrella policy mechanics vary significantly by carrier and policy language. An attorney should review the specific policy terms.
What to Do If You Think You Have a UIM Claim
If you believe your damages may exceed the at-fault driver’s liability coverage, notify your own insurer promptly. Illinois policies typically require timely notice of a potential UIM claim, and missing a notice deadline can jeopardize your rights. Do not settle with the at-fault driver’s insurer without first obtaining your own insurer’s written consent — settling without consent can trigger a policy exclusion that eliminates your UIM recovery entirely.
Because the underinsured motorist setoff in Illinois operates in ways that are counterintuitive to most people, having an attorney review your declarations page, the at-fault driver’s policy disclosure, and your damages before you settle any portion of the claim can protect substantial sums of money that might otherwise be left on the table.
Talk to a Chicago Attorney — Free Consultation
If you or a family member has been harmed, the attorneys at Phillips Law Offices are ready to help. Call (312) 346-4262 or contact us online for a free, no-obligation consultation. We handle cases throughout the Chicago metropolitan area.
