Oak Park homeowners opening their second-installment property tax bills when they arrive Sept. 1 will see the results of a reassessment cycle that shifted less burden onto residents than the last one did.

New data from the Cook County Assessor's Office shows residential properties now make up 68% of the total assessed value across 13 north and northwest suburban townships, up from 66% before the 2025 reassessment began. That 2-percentage-point shift is half the size of 2022's swing, when the residential share jumped from 63% to 67% after Board of Review appeals.

The difference: commercial properties lost less value on appeal this time. In 2022, Board of Review decisions cut commercial assessed values by 20%. In 2025, that reduction dropped to 14%.

"When big businesses no longer get the same huge cuts as they did before we began our reform of the appeal process, homeowners benefit," Cook County Assessor Fritz Kaegi said in an Aug. 18 statement.

What changed

The smaller shift traces back to a December 2024 county report on commercial valuations, which found north suburban industrial properties were assessed at only two-thirds of their market value after 2022 appeals. The report recommended data-sharing between the Assessor's Office and Board of Review, joint methodology for tax expense estimates and more Assessor staff appearances at appeal hearings.

Those reforms worked. The Assessor's Office prepared individual defenses for 14 large commercial properties, most of them data centers. Four received no reduction at all from the Board of Review, and another four received cuts of less than 25%.

In Elk Grove Village, where many targeted data centers sit, homeowners now hold roughly the same share of the tax base as before the reassessment began.

Still, residential property's share of the north suburban tax base is the highest since the Assessor's Office began tracking the metric in 2019, having risen 11 percentage points over eight years. Kaegi called the data "a promising first step" but said "there's much more that needs to be done."

What Oak Park residents should know

Oak Park Township falls within the 13 north suburban townships covered by the 2025 reassessment. The countywide averages may not reflect Oak Park's specific burden split; township-level data was not included in the Assessor's release.

Tax bills reflecting the 2025 reassessment values will be mailed Tuesday, Sept. 1, with payment due Thursday, Oct. 1. Property owners can view bills online as of Tuesday, Aug. 18, according to the Assessor's Office.

For context, Oak Park's most recent second-installment bills, issued in late 2025 for tax year 2024, carried an average increase of about 4.5%, driven by a combined $264 million in local levies, according to Oak Park Township.

Meanwhile, the Board of Review began accepting 2026 assessment appeals for Oak Park and River Forest on Monday, Aug. 3, according to the Cook County Board of Review. The Board processed a record 290,533 appeals during tax year 2025.

Oak Park homeowners' 2026 reassessment notices estimated a median single-family home value of $559,000, according to county valuation data. Those values will appear on 2027 tax bills, not the Sept. 1 bills.