What Is Underinsured Motorist (UIM) Coverage in Illinois and When Can You Use It?
Sat 14 Feb, 2026 / by Robert Parker / Uninsured / Underinsured Motorist Claims
After a serious crash, many injured drivers assume the at-fault driver’s insurance will cover their losses. Unfortunately, that is not always the case. In Illinois, the minimum required liability limits are often far too low to cover serious injuries.
That is where underinsured motorist coverage Illinois comes into play.
Underinsured motorist (UIM) coverage is part of your own auto insurance policy. It protects you when the at-fault driver has insurance — but not enough to fully compensate you for your injuries.
If you live in Peoria or anywhere in Central Illinois, understanding how UIM works could make a substantial difference in your recovery after a crash.
What Is Underinsured Motorist Coverage in Illinois?
Underinsured motorist (UIM) coverage is part of your auto insurance policy. In Illinois, UM coverage is generally required at minimum liability limits, and when UM coverage exceeds those minimums, matching UIM coverage must also be included. It applies when:
- The at-fault driver has liability insurance, and
- Their policy limits are insufficient to cover your total damages.
In Illinois, drivers are required to carry minimum liability limits of:
- $25,000 per person
- $50,000 per accident
These limits are often inadequate in cases involving surgery, permanent injury, or extended hospitalization.
How UIM Differs from Uninsured Motorist (UM) Coverage
It is important not to confuse underinsured motorist (UIM) coverage with uninsured motorist (UM) coverage.
- Uninsured Motorist (UM): Applies when the at-fault driver has no insurance at all or is a hit-and-run driver.
- Underinsured Motorist (UIM): Applies when the at-fault driver has insurance, but their limits are too low to fully compensate you.
Both types of coverage are designed to protect you from financially irresponsible drivers, but they apply in different situations.
When Does UIM Coverage Apply?
UIM coverage typically applies when:
- You suffer serious injuries.
- Your damages exceed the at-fault driver’s policy limits.
- You have UIM coverage with limits higher than the at-fault driver’s liability limits.
For example:
If the at-fault driver has $25,000 in liability coverage and your medical bills, lost wages, and pain and suffering total $150,000, their insurance will only pay up to $25,000.
If you carry $100,000 in UIM coverage, your policy may cover additional compensation — up to the difference between your UIM limits and what the at-fault driver paid.
How UIM Claims Work in Illinois
UIM claims involve a two-step process:
- You pursue a claim against the at-fault driver’s liability insurer.
- After exhausting their policy limits, you pursue your UIM claim with your own insurer.
This process can be complex and often overlaps with the broader insurance settlement timeline.
To understand how accident claims generally progress, visit our
insurance settlement timeline page.
The Relationship Between UIM Coverage and Liability Limits
In Illinois, UIM coverage is generally “gap” coverage.
This means your UIM coverage fills the gap between:
- The at-fault driver’s liability limits, and
- Your total damages, up to your UIM policy limits.
For example:
- At-fault driver: $25,000 limit
- Your UIM coverage: $100,000 limit
- Your damages: $150,000
The at-fault driver pays $25,000. Your UIM coverage may provide up to $75,000 additional coverage (the difference between $100,000 and $25,000).
Stacking vs. Non-Stacking Policies
Stacking refers to combining multiple UIM coverages under separate vehicles or policies.
Some Illinois policies allow stacking, meaning:
- You may combine UIM limits from multiple insured vehicles.
Other policies contain anti-stacking provisions, limiting recovery to a single policy limit.
Whether stacking applies depends on the language of your insurance contract. Careful review of the policy is essential.
Common Scenarios Where UIM Coverage Is Critical
- Severe spinal injuries requiring surgery
- Traumatic brain injuries
- Permanent disability
- Multiple injured parties splitting $50,000 limits
In these situations, the at-fault driver’s minimum $25,000/$50,000 limits are quickly exhausted.
To understand how serious injuries affect compensation, see our
car accident settlement value guide.
How to File a UIM Claim
Filing a UIM claim involves:
- Notifying your insurer of the claim
- Providing documentation of damages
- Obtaining consent before settling with the at-fault driver
One critical step: before accepting the at-fault driver’s policy limits, you must notify your UIM carrier and preserve your rights.
Failing to do so may jeopardize your UIM benefits.
Why Your Own Insurance Company May Deny or Undervalue Your Claim
Although it may feel surprising, your own insurer becomes adversarial in a UIM claim.
They may:
- Dispute liability
- Argue your injuries are preexisting
- Challenge the necessity of treatment
- Offer less than policy limits
UIM claims are essentially injury claims against your own insurance company.
If negotiations fail, arbitration or litigation may be required.
The Importance of Legal Guidance Before Accepting a Settlement
Accepting the at-fault driver’s policy limits without proper notice to your insurer can compromise your UIM rights.
Before signing any release:
- Review your UIM coverage limits.
- Provide written notice to your insurer.
- Confirm consent to settle.
For a broader overview of your rights after a crash, visit our
Peoria car accident lawyer page.
Frequently Asked Questions
Is underinsured motorist coverage required in Illinois?
Illinois requires UM coverage at least at statutory minimum limits. Higher UM limits must be offered and may be rejected in writing, and when UM exceeds the minimum, matching UIM coverage is required. Many Illinois drivers carry it because minimum liability limits are low.
Can I use UIM coverage if I was partially at fault?
Illinois follows modified comparative fault rules. Your recovery may be reduced by your percentage of fault.
Does UIM apply if multiple people are injured?
Yes, but the at-fault driver’s per-accident limits may be divided among injured parties, increasing the importance of UIM coverage.
Can my insurance company refuse to pay UIM benefits?
They may dispute the value of your claim, but valid UIM coverage should pay according to the policy terms if damages exceed the at-fault driver’s limits.
Speak With a Peoria Car Accident Attorney
Understanding underinsured motorist coverage Illinois can be the difference between partial recovery and full compensation after a serious crash.
If you believe your damages exceed the at-fault driver’s insurance limits, Parker & Parker Attorneys at Law can review your policy and explain your options.
Parker & Parker Attorneys at Law
300 NE Perry Ave
Peoria, IL 61603
Phone: 309-673-0069
Contact us today for a free consultation.
If you or a loved one has been injured in a car accident, the experienced Peoria personal injury attorneys are ready to help you pursue the compensation you deserve.