Stacking UM/UIM Coverage in Illinois

When you carry multiple auto insurance policies—or a single policy covering multiple vehicles—you may be able to stack your uninsured and underinsured motorist (UM/UIM) coverage to increase the amount of compensation available after a serious crash. Illinois law permits stacking in certain circumstances, but insurance companies routinely draft policy language designed to limit or eliminate this right.

At Parker & Parker Attorneys at Law, we review every UM/UIM policy our Peoria-area clients hold to determine whether stacking applies and whether anti-stacking clauses are enforceable under current Illinois case law.

What Does It Mean to “Stack” UM/UIM Coverage?

Stacking means combining the coverage limits from more than one vehicle or policy to create a larger pool of UM/UIM benefits. Illinois recognizes two forms:

• Intra-policy stacking — Adding the UM/UIM limits for each vehicle insured under a single policy. If you insure three vehicles with $100,000 per-person UM limits, stacking could provide up to $300,000 in coverage.
• Inter-policy stacking — Combining UM/UIM limits from separate insurance policies, such as a personal auto policy and a separate umbrella or excess policy.

Illinois Law on UM/UIM Stacking

Under 215 ILCS 5/143a, Illinois insurers must offer UM/UIM coverage in amounts up to the bodily injury liability limits of the policy. The statute does not expressly prohibit stacking, and Illinois courts have addressed the issue in several key decisions:

• Hobbs v. Hartford Insurance Co. of the Midwest — The Illinois Supreme Court examined whether anti-stacking provisions in UM endorsements are enforceable, finding that clear and unambiguous anti-stacking language may limit recovery, but ambiguous language is construed in favor of the insured.
• Katzenbach v. State Farm — Reinforced that anti-stacking clauses must be conspicuous and clearly written; buried or confusing language may not prevent stacking.

The practical effect: whether you can stack depends heavily on your specific policy language. Many Illinois drivers are entitled to stacking but never realize it because their insurer’s anti-stacking clause is either ambiguous or improperly applied.

When Stacking Makes the Biggest Difference

Stacking is most valuable when the at-fault driver’s liability insurance is insufficient to cover your damages and your own UM/UIM coverage from a single vehicle is also inadequate. Common scenarios include:

• Multi-vehicle households — Families insuring two or more vehicles under one policy may stack limits across all vehicles.
• Severe injuries with high medical costs — Traumatic brain injuries, spinal cord damage, or long-term rehabilitation costs that exceed a single vehicle’s UM limit.
• Hit-and-run crashes — Where the at-fault driver is never identified and your UM coverage is the only source of recovery.
• Minimum-coverage at-fault drivers — Illinois minimum liability limits are just $25,000 per person. If the at-fault driver carries only minimum coverage, stacking your UIM limits can dramatically increase available compensation.

Anti-Stacking Clauses: What to Watch For

Most Illinois auto policies contain language limiting UM/UIM benefits to the highest single limit, regardless of how many vehicles are insured. These anti-stacking provisions are not automatically enforceable. Our attorneys analyze:

• Whether the anti-stacking language is clear and unambiguous
• Whether the insured was given a meaningful choice at the time of purchase
• Whether the clause conflicts with Illinois public policy under 215 ILCS 5/143a
• Whether separate premiums were charged for UM/UIM coverage on each vehicle

If you paid separate UM/UIM premiums for each vehicle on your policy, there is a strong argument that you purchased separate coverage for each vehicle and should be permitted to stack.

How Parker & Parker Can Help

Insurance companies rarely volunteer that stacking is available. Our Peoria personal injury attorneys:

• Obtain and review every applicable insurance policy—yours, household members’, and any umbrella or excess policies
• Identify ambiguous anti-stacking language and challenge its enforceability
• Calculate the maximum UM/UIM recovery available through stacking
• Negotiate with or arbitrate against your insurer to recover full stacked benefits

If you have been seriously injured by an uninsured or underinsured driver in Peoria or central Illinois, contact Parker & Parker for a free consultation. We will review your policies and determine whether stacking can increase your recovery.

Frequently Asked Questions

Can I stack UM/UIM coverage across different insurance companies?

Potentially, yes. Inter-policy stacking may apply when you hold auto policies from multiple insurers, though each policy’s language and Illinois case law govern whether stacking is permitted.

Does stacking increase my premiums?

Not directly. Stacking uses coverage you have already purchased. However, if you paid separate premiums for each vehicle’s UM/UIM coverage, that strengthens your stacking argument.

My policy says stacking is not allowed. Is that the final word?

Not necessarily. Illinois courts have invalidated anti-stacking clauses that are ambiguous, buried in fine print, or that conflict with the purpose of the UM/UIM statute. An attorney can evaluate your specific policy language.

How do I know if I’m paying separate premiums for each vehicle?

Check your policy declarations page. If UM/UIM coverage is listed separately for each vehicle with a corresponding premium, you may have grounds to stack.