A Cook County appeal can be argued in October, decided in December, and appealed to the state the following spring. None of those dates matter to the value. Illinois assesses property as of January 1. So a retrospective appraisal tax appeal has one effective date, fixed by statute, whether the hearing lands eight months later or eighteen. The most common way a strong appeal loses is not a bad comparable. In practice, it is an appraisal dated the wrong day.
- Where the January 1 date comes from and what the Board of Review and PTAB do with it
- How an appraiser rebuilds a January 1 value from evidence that arrives months later
- Why a refinance or purchase appraisal with the wrong date can sink an otherwise good case
Where the January 1 Date Comes From
The rule is in the Property Tax Code. Under section 9-155, the assessor determines the value of each property “as of January 1 of that year.” So everything downstream inherits that date. The assessment is a fraction of fair cash value on January 1. The Board of Review decides whether that fraction is right on January 1. Then the Property Tax Appeal Board, if the case gets that far, rules on the same day’s value.
Cook County adds a wrinkle that makes the date carry more weight, not less. The county reassesses on a three-year cycle, township by township. We covered that cycle in our piece on the 2026 south suburbs reassessment. A value set as of January 1 in a reassessment year becomes the base for the next two years’ bills. So get that one date right and the benefit compounds. Get it wrong and so does the cost.
What a Retrospective Appraisal Tax Appeal Has to Prove
The PTAB’s own rules spell out what counts as proof of market value. Under 86 Ill. Adm. Code 1910.65, the Board will look at an appraisal of the subject “as of the assessment date at issue.” It will also look at a recent sale of the subject, at construction costs if the build date is close to the assessment date, or at three or more comparable sales with support for their similarity. Every one of those is anchored to the same January 1.
The same Part makes PTAB proceedings de novo. The Board considers only what is submitted to it, and gives no weight to what happened at the Board of Review. So an appraisal that carried the day at the county level has to be filed again at the state level. And an appraisal never dated to January 1 does not improve by being resubmitted. Our article on Board of Review evidence rules covers the county-level requirements in detail.
Also, the word “retrospective” describes the work, not the report type. By the time an appeal is heard, January 1 is in the past. The appraiser has to establish what a buyer and seller would have agreed to on that date, using only what was knowable then. That is a different discipline from a current-value appraisal. It shows most in the comparable selection.
Rebuilding January 1 From Evidence That Arrives Later
Consider a hypothetical Northbrook house reassessed for 2026. The appeal is filed in the fall, so the hearing sits well past the date. By then the appraiser can see sales from November 2025, February 2026, and June 2026. The November and February sales bracket the date and need only a small market conditions adjustment to land on January 1. The June sale is a different matter. If the market moved between January and June, the adjustment has to run backward to the effective date. The report should say how the appraiser measured that movement.
Physical condition follows the same logic, too. A roof that failed in March does not lower the January 1 value. A basement that flooded in December 2025 does. Permits, listing photos, inspection reports, and the property record card all help establish what the house looked like on the first of the year. In Cook County the record card also shows the characteristics the assessor used. So errors in living area, age, or condition rating are among the cleanest grounds for a change. They go to the assessor’s own inputs on the assessor’s own date.
Sales of the subject, meanwhile, deserve their own note. A closing near January 1 is powerful evidence, and both the PTAB rules and most county boards treat it that way. A closing well after the date is still useful, but it has to be adjusted back. The further it sits from January 1, the more the argument depends on the adjustment rather than the price.
The Refinance Appraisal Problem
Tax consultants running volume appeals see this one constantly. An owner refinanced in May, has a lender’s appraisal in hand, and wants to use it. The report is competent, of course. It is also dated May, prepared for a lender, with an intended use of mortgage lending. Submitted as-is, it invites the obvious objection. This is not a January 1 value, and it was not prepared for this purpose.
The fix is not to throw the report away. Instead, ask the appraiser, or a new one, for a retrospective value as of January 1 with the appeal as the stated intended use. Then the lender’s report becomes source material for condition and characteristics. The new report supplies the date and the purpose. For a consultant managing dozens of parcels, check the effective date and intended use on every appraisal before filing. That two-minute step will save more cases than any other.
Other States, Same Date
January 1 is not an Illinois quirk. Florida assesses as of January 1 as well, and its Value Adjustment Board petitions turn on that date the same way. Texas uses January 1 for most property as well. The mechanics of the appeal differ from state to state. But the appraiser’s task is the same everywhere PahRoo works: find the value on the lien date, not the hearing date.
The divorce lane has its own version of this problem, where the date is chosen rather than fixed. We covered that in our article on the date of value in a divorce appraisal. The tax version is simpler in one way and harder in another. Simpler, because nobody argues about which date applies. Harder, because evidence keeps arriving after the date has passed, and the appraiser has to keep it out.
Check the Date Before You Check the Number
Before an appraisal goes into an appeal file, confirm three things on its first page. The effective date is January 1 of the assessment year at issue. The intended use names the assessment appeal, not a loan. And the comparable sales either bracket the date or carry a stated market conditions adjustment back to it. If any of the three is missing, then the number on the cover is answering a question the Board did not ask. So fix the date first. The value follows.
Is Your Client’s Appraisal Dated January 1?
PahRoo prepares retrospective appraisals as of the assessment date for Board of Review and PTAB appeals, with the intended use and adjustments the rules expect.
Frequently Asked Questions
What date does an Illinois property tax appraisal have to use?
January 1 of the assessment year at issue. Section 9-155 of the Property Tax Code sets the assessor’s valuation date at January 1, and the PTAB rules describe acceptable proof of value as an appraisal “as of the assessment date at issue.” An appraisal dated any other day is answering a different question.
Can I use a refinance appraisal for a tax appeal?
Usually not as-is. A lender’s appraisal carries the lender’s effective date and an intended use of mortgage lending. It can be useful source material for condition and characteristics, but the appeal needs a report with a January 1 effective date and the assessment appeal named as the intended use.
What is a retrospective appraisal?
An appraisal with an effective date in the past. The appraiser estimates value as of that earlier date using only information a market participant could have known at the time, and adjusts later evidence back to the date. Every tax appeal appraisal is retrospective, because January 1 has passed by the time the appeal is heard.
Do sales after January 1 count in a tax appeal?
They can, with care. A sale shortly after the date is often the best evidence available, and it can be adjusted back to January 1 for any market movement in between. The further a sale sits from the date, the more the argument depends on the adjustment rather than the price, and the report should show how the adjustment was measured.
Does the PTAB accept the appraisal I filed with the Board of Review?
Only if you file it again. PTAB proceedings are de novo under 86 Ill. Adm. Code 1910.50, which means the Board considers only the evidence submitted to it and gives no weight to what the county board decided. The appraisal must be part of the PTAB record on its own.
January 1 Valuations for Illinois Appeals
Property tax attorneys and consultants across Cook County and the collar counties rely on PahRoo Appraisal & Consultancy for retrospective appraisals dated to the assessment year. Our MAI and SRA designated team prepares reports for Board of Review and PTAB filings as part of our appraisal services, and our property tax appeal FAQs cover what clients ask first. To discuss a parcel or a portfolio, contact our team.