Illinois Commercial Lease CAM Disputes: The 10-Year Recovery Window

Illinois gives commercial tenants more time to recover CAM overcharges than any other state in the country. Ten years. That is the statute of limitations for written contract claims under 735 ILCS 5/13-206, and your commercial lease is a written contract. Most tenants assume the window is three or four years, because that is what they have heard, or because their attorney in another state told them that. In Illinois, that assumption costs money.

This matters because CAM overcharges are rarely caught in the first year. The management fee creeps past the lease cap in year two. The base year gross-up error compounds quietly through years three and four. By the time a tenant suspects something is wrong, often because they hired a new CFO or switched property managers and someone finally looked at the reconciliations, they may be in year six or seven of the lease. In California or Texas, that tenant has lost the early years. In Illinois, they have not.

This guide explains how the 10-year window works, when it can be extended further, and what dollar difference it makes in practice.

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The statute: 735 ILCS 5/13-206

The operative text is short: Illinois law provides a 10-year limitation period for actions on written contracts. The full citation is 735 ILCS 5/13-206.

The distinction that trips up tenants and their attorneys: 735 ILCS 5/13-205 provides a five-year period for "all civil actions not otherwise provided for." If someone reads only that provision and stops there, they get the wrong answer for written contracts. Your commercial lease is a written contract, and 735 ILCS 5/13-206 gives you 10 years.

Comparison of Illinois SOL provisions:

If someone tells you your CAM claim is subject to a five-year limit in Illinois, ask them whether they are applying 13-205 to a written contract. The answer is that 13-206 controls for written agreements.

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What the 10-year window means in dollars

The recovery difference between Illinois and a four-year SOL state on the same overcharge is not abstract. Here is a concrete illustration:

A tenant in a 2,000 SF Chicago retail space pays $10 per SF in CAM annually ($20,000/year). Their landlord has been applying a systematic 5 percent overcharge through management fee stacking, a practice where a property management fee and a separate asset management fee each pass through when the lease only permits one. The combined cap is 5 percent of CAM; the landlord bills 7.8 percent. That 2.8 percent excess on a $260,000 CAM pool means the tenant's share of the excess is approximately $1,400 per year ($260,000 x 2.8% x 19.2% pro-rata share, roughly). Call it $1,000 per year in excess management fees for simplicity.

Same lease. Same error. Same tenant. Illinois is worth 2.5 times the four-year SOL states on this error alone.

Now scale to a larger tenant. A 5,000 SF Chicago office tenant paying $11 per SF in CAM ($55,000 per year) with a base year error that generates $8,000 per year in excess billings:

The base year error in this example: the building was at 55 percent occupancy in 2019, which the landlord used as the base year. Under a properly functioning gross-up clause, the landlord should have normalized base year expenses to a 95 percent occupancy equivalent before establishing the baseline. Because they did not, every subsequent year's escalation is measured against an understated base. The tenant is paying $8,000 more per year than they would if the gross-up had been applied correctly.

CAMAudit detects this under Rule 7 (Base Year Error) by comparing the stated base year expenses to what they should have been under a normalized occupancy gross-up.

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The base year gross-up issue in Chicago commercial real estate

Chicago's office market had a significant occupancy disruption in 2019 through 2021. Many leases executed in that window used 2020 or 2021 as base years, when buildings were operating at 40 to 60 percent of normal occupancy. Expenses that scale with occupancy, HVAC, janitorial, utilities, were correspondingly low. Landlords who did not gross up these base year expenses to a normalized 95 percent occupancy equivalent built in an overcharge that compounds every year.

The practical effect: suppose base year janitorial was $180,000 in 2020 (at 50% occupancy). Normalized, it should have been approximately $340,000. The tenant's annual escalation is measured against $180,000 instead of $340,000. By year five, on a 3 percent annual increase, the excess annual billing is $20,000 or more for a mid-size tenant. Over 10 years in Illinois, that is $200,000 in recoverable overcharges.

These errors are not caught by tenants who simply pay the reconciliation. They are caught by running the math on what the gross-up should have produced.

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The account stated doctrine: why you must object annually

Illinois recognizes the account stated doctrine in commercial contexts. If a creditor (here, your landlord) renders a statement of account and the debtor (you) pays it without objection, the payment can be treated as acceptance of the account as stated. This is a defense landlords raise when tenants bring CAM claims years after paying reconciliations without protest.

The account stated doctrine does not automatically defeat a 10-year claim. But it creates a factual argument that consistent payment without objection constitutes acquiescence to the amount charged. Illinois courts have allowed account stated arguments in commercial contexts where there was a course of dealing involving regular statements and payments.

The strategic response: document your objection in writing every year, even if you are not yet prepared to file a formal dispute. A written objection sent by certified mail prevents the account stated defense from attaching to that year's charges. It does not need to be a formal legal demand; a letter stating "We are reviewing the 2024 CAM reconciliation and reserve all rights to dispute any charges upon completion of our review" is enough to interrupt the account stated argument for that year.

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The discovery rule: potential extension beyond 10 years

Illinois applies the discovery rule to some contract claims. Under this doctrine, the statute of limitations does not begin to run until the plaintiff knew or should have known that a cause of action existed. For CAM disputes, this is a nuanced question.

If the overcharge is apparent from the reconciliation statement itself, such as a management fee that is plainly above the lease's stated cap, the SOL likely runs from delivery of that statement. A tenant who receives a reconciliation showing 8 percent management fee when the lease caps it at 5 percent "knew or should have known" about the claim.

But if the overcharge requires access to information the tenant does not have, for example, the landlord's total CAM pool that is not disclosed on the statement, or a pro-rata calculation error that depends on knowing the total building GLA as applied to all tenants, Illinois courts have sometimes held that the discovery rule tolls the SOL until the tenant had access to the underlying data. This is not a guaranteed extension, and it depends heavily on what information was disclosed and when, but it is a recognized argument under Illinois law.

Practical implication: if you can show you had no reasonable way to know about the overcharge until you received records in response to an audit request, Illinois law may support tolling the 10-year period from the date of that disclosure rather than the date of the original reconciliation statement.

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Illinois-specific considerations for dispute strategy

Illinois has no commercial tenant anti-retaliation statute. Challenging your CAM reconciliation does not trigger any statutory protection if the landlord decides to become difficult. Use collaborative or neutral dispute letter tone unless the lease relationship is already adversarial.

Chicago courts apply plain contract interpretation and are experienced with commercial lease disputes. Clear lease exclusion language is enforced. If your lease says management fees cannot exceed 4 percent of gross revenues, a fee that exceeds that cap is a breach, and an Illinois court will say so without much equivocation.

For large multi-tenant buildings managed by institutional landlords, the pro-rata share denominator issue is particularly common. CAMAudit detects Rule 4 (Pro-Rata Share Error) by comparing the stated GLA denominator in the reconciliation to the actual total GLA including all premises, anchors, and excluded spaces. In Chicago's large Class A towers and mixed-use developments, this calculation is frequently wrong in the landlord's favor.

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Worked example: Chicago office tenant, base year gross-up failure

Setup: 5,000 SF office tenant in a 200,000 SF building in Chicago's West Loop. Lease executed January 2021, base year 2020. CAM per SF capped at 5 percent annual increase over prior year. Building was at 52 percent occupancy in 2020.

The error: 2020 base year expenses were not grossed up to 95 percent occupancy. Actual 2020 expenses: $1,600,000. Normalized to 95 percent occupancy: $2,880,000 (using a linear scaling for occupancy-variable costs; approximately 70 percent of the expense pool scales with occupancy).

Effect on tenant:

Under the Illinois 10-year SOL, the tenant can recover errors going back to 2021 through 2031. The full 10-year recovery, assuming the error persists, could reach $100,000 or more. In a four-year SOL state, the same tenant would be limited to approximately $40,000.

CAMAudit flags this under Rule 7 by computing what base year expenses should have been at normalized occupancy and comparing the escalation trajectory to what it would have been under a correctly grossed-up base.

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Illinois SOL and key statutes reference

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FAQ

Does the 10-year SOL under 735 ILCS 5/13-206 apply specifically to CAM disputes?

Yes, assuming your dispute arises from a written commercial lease. A CAM overcharge is a breach of the lease contract. The lease is a written contract. Illinois applies 735 ILCS 5/13-206 (10-year period) to written contract claims. Your CAM dispute falls within that framework. The longer five-year provision under 13-205 applies to unwritten contracts and does not control when a written agreement governs the relationship.

What if my lease has a 90-day dispute window? Does Illinois law override it?

No, and this is a critical point. The 10-year SOL sets the outer limit for a legal action. It does not override a contractual condition precedent in the lease that requires you to object within 90 days of receiving the reconciliation. If your lease says you must object within 90 days or waive your right to dispute, Illinois courts generally enforce that condition. The SOL and the lease-defined dispute window operate independently: you must satisfy both to preserve a viable claim. Miss the 90-day contractual window and the 10-year SOL becomes irrelevant for that year.

Can I use the Illinois discovery rule to extend my window beyond 10 years?

Potentially, in specific circumstances. The discovery rule tolls the SOL from the date you knew or reasonably should have known about the overcharge. If the overcharge was apparent from the reconciliation itself, courts will not toll the period: you "should have known" when you received the statement. If the overcharge depends on information the landlord did not disclose, such as the actual CAM pool denominator or the component breakdown of management fees, there is a stronger argument that the SOL tolled until you received that information through an audit request. This is a fact-specific argument, and you should consult an Illinois attorney before relying on it as a planning tool.

What is the account stated doctrine and how does it affect my Illinois claim?

The account stated doctrine is a defense landlords raise when a tenant has consistently paid reconciliation statements over many years without objection. The argument is that the pattern of payment without protest constitutes implicit acceptance of the amounts as correct, which can function as a bar to later claims. Illinois courts have allowed this defense in commercial contexts. The counter is simple: send a written annual objection or reservation of rights each year, even before you have reviewed the reconciliation in detail. This prevents the account stated argument from attaching. A one-paragraph letter by certified mail is sufficient.

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Related Resources

• CAM Recovery Guide : How commercial tenants recover CAM overcharges, with step-by-step process and state lookback windows

• Base Year Error: How an Understated Gross-Up Costs Tenants Thousands

• Management Fee Overcharge in CAM: Stacking, Caps, and What to Look For

• Pro-Rata Share Errors: The Most Common CAM Math Mistake

• CAM Audit Cost: Big Four vs. Boutique vs. AI

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Frequently Asked Questions

This article is for informational purposes only and does not constitute legal advice. Statute of limitations, discovery rules, and lease enforcement vary by specific facts and jurisdiction. Consult a licensed Illinois attorney for advice specific to your situation.