The property tax figure on a South Barrington listing sheet this fall may already be out of date. The tax year 2025 bills went online August 18 and had to be paid by October 1, 2026. Across Cook County, the Treasurer reports that South Barrington's median homeowner bill rose 16.4% from the year before. That was the largest median increase among the four Cook County villages served by Barrington Unit School District 220. Because of how Cook County bills taxes, the new number will set part of what owners pay next year too.
Most people credit the increase to the school referendum. The referendum is part of it. But the figures the district gave voters in 2024 don't come close to a 16.4% median increase. The rest came from a change in how South Barrington homes are valued compared with everything else that pays into the same levies.
The bill that sets next spring's bill
Cook County splits each year's taxes into two installments, and they don't work the same way. The Cook County Assessor's Office explains that the first installment is exactly 55% of the previous year's total tax. Taxes are billed the year after the tax year they cover. So the tax year 2026 first installment, due in 2027, will be 55% of the tax year 2025 total that South Barrington owners just paid.
Late bills make the timing harder to follow. The Daily Herald reported in June that Cook County's second-installment bills, normally mailed in July and due in August, would run about two months late again because of the county's technology overhaul. It also noted that the previous year's second installments did not go out until November. In 2026 the sequence went like this:
- August 18, 2026: Tax year 2025 second-installment bills become viewable online.
- September 1, 2026: Bills are expected in the mail. The Assessor's Office announces them as released that day.
- October 1, 2026: Payment due.
If you are comparing homes this November, a tax figure pulled from a listing written before August may reflect the tax year 2024 bill. The tax year 2025 bill is the one that carries forward.
What voters were told the bond would cost
On November 5, 2024, voters approved Barrington 220's $64 million bond referendum. The district's projects include safety and security upgrades, a new community auditorium at Barrington High School, STEAM and instructional spaces, middle school science labs, fine arts and music improvements, mechanical systems, and new windows, doors and flooring. In its June 2026 update, the district reported that groundbreaking on the auditorium was complete. Its project status page lists the auditorium and the windows, doors and flooring work in the build phase.
The district put the cost at an additional $236 per year for the average household, based on a $500,000 home's market value, over 20 years.
That $500,000 example is a lot smaller than a typical home here. In 2025, the Assessor estimated the median market value of single-family homes across Barrington Township at $803,000. A larger home pays a larger share of the bond, so the referendum cost for many South Barrington owners is more than $236. Even so, a bond priced in the hundreds of dollars a year doesn't explain a 16.4% increase in the median bill on its own. The Treasurer's tax year 2025 analysis names a second cause. In Barrington Hills, South Barrington, Inverness and Barrington, "home values in those suburbs grew at quicker pace than business values."
A tax bill is a share of a fixed amount
Your bill is not your home's value multiplied by some set percentage. Each taxing body sets a levy, which is the total dollar amount it asks for. As the Cook County Treasurer explains, the Clerk then sets tax rates so that assessed value multiplied by the rate equals the levy. When every property's value rises, rates fall to make up for it.
District 220 describes the same mechanism on its own tax levy page. Under the state's tax cap law, increases in the district's levy are limited to 5% or the Consumer Price Index, whichever is lower, with new construction as the one exception. County clerks then divide the levy among owners by each property's percentage of the district's total value. The district puts it plainly: "Some property owners may see a smaller increase or a decrease in their tax bill, while others may see a larger increase depending on each homeowner's property value relative to all other property values."
So a higher assessment doesn't raise your bill by itself. Your bill goes up when your assessment rises faster than everyone else's in the same district.
South Barrington's assessments rose faster than most
Cook County reassesses each township once every three years. Barrington Township's initial 2025 values came out on July 3, 2025. Across the north and northwest suburbs, median residential assessed values rose 20%. Among the municipalities with the largest increases in that region, the Treasurer lists all three Cook County villages around Barrington.
| Cook County portion | Median residential assessed value, 2024 | Median residential assessed value, 2025 | Change in assessed value | Change in median homeowner bill, tax year 2025 |
|---|---|---|---|---|
| Barrington Hills | $71,965 | $95,000 | +32.01% | +15.0% |
| South Barrington | $76,000 | $99,000 | +30.26% | +16.4% |
| Inverness | $53,459 | $69,320 | +29.67% | +12.2% |
| Barrington | not in the Treasurer's top list | not in the Treasurer's top list | not in the Treasurer's top list | +11.5% |
The state's adjustment wasn't behind the change. The Illinois Department of Revenue set Cook County's final equalization factor at 3.0300 for 2025, compared with 3.0355 for 2024. Nearly all of the 30% rise in South Barrington's median assessed value came from the reassessment itself.
Business property did not keep pace. After all appeals in the north and northwest suburbs, the assessed value of homes rose 24.4%, while commercial property rose 7.9%. The Assessor's Office reports that the residential share of total assessed value in the region rose from 66% before the reassessment to 68% after Board of Review appeals. When homes make up a bigger share of the total, homes pay a bigger share of each levy, even if the levies grow only modestly.
That explains how South Barrington's median bill could rise 16.4% while total taxes across the north and northwest suburbs rose 6.4% and the regional median homeowner bill rose 6.7%, to $8,007. Residential taxes across the region rose 9.9%, faster than taxes overall. The bond added new dollars to the levy. The reassessment moved a bigger share of every levy onto homes, and South Barrington's homes rose in value faster than the region's median.
What this means when you compare villages
Two things matter for a buyer or seller looking at South Barrington this winter.
The first is that the increase is now built into the base. Barrington Township's next scheduled reassessment falls in 2028, three years after the 2025 cycle. Until then, assessments in the township generally stay where the 2025 reassessment put them, and the 2027 first installment follows the 55% rule. Those rules decide how much the tax year 2025 bill affects next year's carrying costs.
The second is that 16.4% is the change for the median South Barrington home. District 220's own explanation means two neighbors can see quite different changes if their assessments moved by different amounts. The bill attached to a specific property identification number tells you more about that home than the village figure does. The Assessor's Office also used the September 1 bill release to remind homeowners to check that they are receiving the exemptions they qualify for. How exemptions apply to any one household is a question for that household's tax professional.
Quick answers
Did the referendum alone cause the increase? No. The Cook County Treasurer attributes the increases in South Barrington, Barrington Hills, Inverness and Barrington partly to the $64 million District 220 bond and partly to home values rising faster than business values.
When was the tax year 2025 bill due? October 1, 2026. The bills went online August 18 and were expected in the mail September 1.
How is the 2027 first installment calculated? It is exactly 55% of the previous year's total tax, according to the Cook County Assessor's Office.
When is Barrington Township reassessed next? Cook County reassesses each township once every three years, and Barrington Township's last reassessment was in 2025. On that schedule, the next one comes in 2028.
This post is general information about how Cook County bills property taxes. It is not legal, tax or financial advice, so please confirm your own situation with a qualified tax professional or attorney.
If you're thinking about selling in South Barrington, your current tax bill is part of how buyers judge your price, and the figure on your listing should be the current one. The Tara Kelleher Team can put together a valuation that reflects the tax year 2025 numbers and a staging plan that helps your home show its value. Get your home valuation and staging plan.
