Homeowners in Northwest Cook County can expect an average bump of about $560 on property tax bills that will go out later this month.

That's based on tax rate and reassessment values released Tuesday by County Clerk David Orr's office.

Orr's data showed the average property tax bill is expected to increase by 6.5 percent throughout the northern part of the county, but homeowners in many suburbs are likely to see much higher increases to tax bills.

The average residential property value for the area increased 14.4 percent over last year, up to $299,100 from $261,500. But the average tax rate fell only by 13 percent. In addition, the county's equalization factor -- set by the Illinois Department of Revenue -- was increased 5 percent from the previous year, which also inflates the taxable value of a property.

"It's going to be devastating to a lot of people," said Elk Grove Township Assessor Connie Carosielli. "Seniors get horrified when they see their bills. We see a lot of tears."

The owner of a $300,000 house in Elk Grove Village can expect to pay an additional $650 in property taxes this year to about $7,270, 9.9 percent more than last year, according to Orr's figures. Only taxpayers in Rosemont, which abates most or all of its property taxes each year, and the Cook County portion of Bensenville have a higher percentage increase to their tax bills this year.

Cook tax rates

Unlike residential property owners in the Northwest suburbs, commercial property owners could see a reduction in their tax bills because those property values rose less than 5 percent over last year, according to Orr's figures.

Carosielli said she'll likely bring in additional staffing to assist in dealing with expected hordes of angry taxpayers who will show up as soon as the tax bills are mailed out at the end of this month.

"Usually we find about 15 percent of those who applied for some type of exemption didn't get the credit on the tax bill and we can help them lower their bill that way," she said.

Unlike township assessors everywhere else in the state, Cook County's township assessors don't have anything to do with setting the assessed value of properties. Instead, they act as taxpayer advocates, help make sure residents are getting exemptions they are entitled to, and help taxpayers appeal their assessments at the board of review.

Cook County Assessor Joe Berrios is responsible for actually assessing the county's properties. Reassessments are done every three years.

Only taxpayers in Barrington Hills, Elgin and Streamwood can expect lower-than-average increases to their property tax bills, according to Orr's figures. Homeowners in the Cook County portion of those towns will see average tax bill increases of 4.2 percent, 5.7 percent and 6.4 percent, respectively.

Tax bills are due Aug. 1.