So your Cook County property tax appeal was denied. Here's what to do

The Cook County Assessor's Office came up with a wildly inflated assessment of my home's value and denied my appeal using inaccurate data.

Why it matters: CCAO officials aren't sure how many others were denied appeals using flawed data. And the only way most homeowners can even see the evidence used for their denials is by filing a Freedom of Information Act (FOIA) request.

What's happening: Today I'm sharing how to file a FOIA request so any homeowners in similar situations can check the quality of evidence used in denying their appeal.

• Also called: Fun in Nerdland.

How it works: Folks who get their triannual assessment and believe it inaccurately reflects their home's characteristics or inflates its value more than 10% above a likely current sale price are encouraged by the CCAO to file an appeal (individually or with a lawyer) by the deadline listed on the notice.

• If the CCAO denies that appeal, the office will offer a brief reason but no evidence to support it. That's where FOIA comes in.

The process: To ask for the evidence, go to the CCAO records site and create an account with an email and password.

• Click "Request Records."
• Under "Types of Reports," click "other" both times.
• Supply information including your address, township, assessment year and property index number.
• In the "Describe records request" box write: All information used to support the denial of my property tax appeal for [ADDRESS], including any homes of comparable age, size, price and quality nearby.

The rules: After filing, the CCAO will send a message saying, "We will monitor all FOIA requests and fulfill them as we are able."

• By Illinois law, however, the agency must respond to your request within five business days or request an extension.

What's next: Tomorrow we'll explore whether it makes sense to hire a lawyer for your tax appeal, and then what the Cook County Assessor's Office is doing to improve its data.

Editor's note: This story is part of a series on Cook County's property tax appeal process. Later this week, we'll explore whether or not it makes sense to hire a lawyer for your tax appeal and what the county assessor's office is doing to improve its data.