What Is the Property Tax Extension Limitation Law?

Illinois’s Property Tax Extension Limitation Law, commonly called PTELL, caps the yearly growth in the total property tax dollars a local taxing district can collect at the lesser of 5% or the prior year’s Consumer Price Index increase. For the 2024 levy year, that ceiling was 2.90%.¹ The nickname “tax caps” is misleading. PTELL does not cap your individual bill and does not cap your property’s assessed value. It limits the total pool of revenue a taxing district draws from all properties combined.² That distinction shapes almost every question homeowners have about the law.

Where the Law Applies

PTELL first took effect for the 1991 levy year in Cook County and the collar counties: DuPage, Kane, Lake, McHenry, and Will. Starting with the 1995 levy year, it extended automatically to non-home-rule districts in any county with 3,000,000 or more residents or any county touching such a county.³ Any other county can adopt PTELL by referendum. The county board places the question on the ballot at a regular election by resolution passed at least 79 days beforehand, and if a majority approves, the law kicks in for levies made after January 1 of the following year.² As of 2025, 39 counties are covered through either the original mandate or a later referendum.

Only non-home-rule districts sit under the cap. Home rule municipalities set their own levies without being bound by the formula. Park districts, library districts, school districts, and fire protection districts almost always fall on the non-home-rule side, which is why PTELL matters most for those bodies. Special service area levies are also excluded.⁴

When a taxing district crosses county lines, PTELL applies only if every county it overlaps has held a referendum and a majority of the district’s equalized assessed value sits in counties where voters approved it. Once that threshold is met, the whole district is covered, including the portion in a county where the referendum failed.²

How the Cap Is Calculated

An “extension” is the actual dollar amount a taxing district receives from the county clerk each year to fund its operations. PTELL restricts the annual increase in that total extension to the lesser of 5% or the CPI change for the 12-month period preceding the levy year.⁵ When inflation runs at 2.9%, that is the ceiling regardless of what happened to property values. A district cannot capture a windfall because homes in the area jumped 10% in a hot market.

The county clerk applies a limiting-rate formula published by the Illinois Department of Revenue.⁶ The numerator is the prior year’s total billed taxes (the aggregate extension base) multiplied by one plus the inflation factor. The denominator is the district’s current equalized assessed value with new property, annexed property, recovered value from expired Tax Increment Financing districts, and disconnected property removed. Stripping those additions out of the denominator keeps them from artificially shrinking the limiting rate, which is how the law lets districts still tax genuinely new value.

If a district’s requested levy would produce a rate above the limiting rate, the county clerk must reduce the levy proportionally across the district’s funds to bring it into compliance.⁷ The district cannot override that reduction on its own.

Why Your Bill Can Still Rise More Than the Cap

This is where most homeowners get tripped up. PTELL limits the total dollars a district collects, not what any single property owner pays. Your bill depends on how your property’s assessed value compares to every other property in the district. If your home’s assessment climbed faster than the district average, you absorb a larger share of the pool even though the pool grew only by CPI.

The Illinois Department of Revenue lists several other reasons a bill can outpace the cap:²

Your bill reflects every district that covers your property, and any home rule municipality on that bill is not bound by PTELL at all.
Voters may have approved higher rates, bond issues, or an increased extension limitation.
A homestead exemption or other reduction you previously received may have been removed, raising your taxable value.
A property that was under-assessed compared to neighbors will see a bigger correction at reassessment, shifting more of the burden onto it.
When other properties in the district lose value, the remaining properties pick up a greater share of the district’s total extension.

PTELL protects against runaway district spending. It does not protect against shifts in how the burden is distributed among individual parcels.

What Sits Outside the Cap

Certain kinds of value growth let a district collect revenue above the standard inflation-adjusted ceiling without asking voters.

New Property

New property under PTELL includes new construction, additions or improvements that raise a parcel’s assessed value, and previously tax-exempt property returning to the rolls. It also covers increases in assessed value from new oil or gas production under the Hydraulic Fracturing Regulatory Act.⁸ Because new property is subtracted from the denominator, a district can tax it on top of the capped extension for existing property. New construction brings new demand for services, and the law lets districts fund that demand.

Annexations and Expired TIFs

When a district annexes land, the equalized assessed value of that land is treated like new property in the formula, giving the district additional revenue to serve the larger territory. The same idea applies when a Tax Increment Financing district expires. While a TIF is active, growth in property values inside its boundary is captured to repay development costs rather than flowing to overlapping taxing districts. When the TIF closes, that value returns to the general tax base at current market rates and sits outside the cap.⁹ Where a large TIF winds down, this can be a substantial boost that requires no referendum.

Voter-Approved and Older Bond Debt

Not every dollar a district levies counts toward the aggregate extension. The statute carves several debt-related items out of the calculation.¹⁰ Debt service on general obligation bonds approved at referendum is entirely outside PTELL, which is the primary tool districts use to fund large capital projects without eating into operating budgets. Principal and interest on general obligation bonds issued before October 1, 1991, and any bonds refunding those, are excluded. Bonds issued to refinance previously voter-approved debt also stay outside the cap. Revenue bonds issued before October 1, 1991, and backed by a property tax levy are exempt, though the district must first exhaust other payment sources.

Non-referendum bonds, sometimes called limited bonds, work differently. Payments on them are subject to a separate debt service extension base that is itself capped, so a district cannot simply issue debt without voter approval to sidestep PTELL.²

How a District Gets Above the Cap

When a district needs more revenue than the standard cap allows, it has to go to the voters. The law provides two referendum paths: one to levy an entirely new tax rate, and another to increase the extension limitation itself for one or more levy years.¹¹ Both must appear at a regularly scheduled election.

Ballot language follows a specific template. For an increase in the extension limitation, the question must state the proposed percentage increase, identify each levy year it would cover, and name the district clearly. The ballot must also show the estimated additional tax on a single-family home with a fair market value of $100,000 for the first affected levy year, along with projections for later years if the increase spans more than one.⁵ A simple majority of voters deciding the question is enough to pass it. If it fails, the district stays under the standard cap. There is no mechanism for the governing board to override a failed referendum.

What This Means in Practice

PTELL forces districts to plan around a predictable revenue ceiling. In years when inflation runs low, that ceiling can be well under 5%. The 2024 levy year cap of 2.90% is typical of recent experience.¹ If pension obligations, labor contracts, or material costs rise faster than CPI, the gap has to come from somewhere: spending cuts, higher service fees, or eventually a referendum.

Districts with little new construction or TIF activity feel the squeeze most, because they cannot lean on the excluded-property provisions to supplement a capped extension. Districts in growing areas have more room, since every new home or commercial building adds to the tax base outside the formula. Over time, that dynamic can produce meaningful funding gaps between stagnant and growing communities operating under the same law.

For homeowners, the practical point is simpler. PTELL slows the growth of total district revenue, but your bill depends on your property’s value relative to your neighbors. Attending assessment hearings and checking your exemption eligibility will do more for what you actually pay than the cap itself ever can.

1
Illinois Department of Revenue. Property Tax – History of CPIs Used for PTELL
2
Illinois Department of Revenue. An Overview of the Property Tax Extension Limitation Law by Referendum
3
Illinois General Assembly. 35 ILCS 200/18-185 – Short Title; Definitions
4
Kane County Clerk. The Property Tax Extension Limitation Law, A Technical Manual
5
Illinois General Assembly. 35 ILCS 200/18-205 – Referendum to Increase the Extension Limitation
6
Illinois Department of Revenue. Property Tax Extension Limitation Law Changes
7
Illinois General Assembly. 35 ILCS 200/18-195 – Limitation
8
Illinois General Assembly. 35 ILCS 200/18-185 – Short Title; Definitions
9
Civic Federation. How Are Local Governments Able to Access Extra Property Tax Revenue from Expiring TIF Districts?
10
Illinois General Assembly. 35 ILCS 200 – Property Tax Code
11
Illinois General Assembly. 35 ILCS 200/18-190 – Direct Referendum; New Rate or Increased Limiting Rate