How property tax is calculated

Start with the value actually used for taxation

Illinois says most property is assessed at one-third of fair market value. Its guidance also identifies exceptions, including Cook County’s classification system. A market-value estimate and a tax assessment therefore should not automatically be compared as identical measures. Official source.

Write down each value with the label shown on the notice: market, appraised, assessed, equalized or taxable. Ask the assessor which measure is the starting point and which adjustments connect it to the next line. Do not multiply a market estimate by a rate quoted for taxable assessed value unless you have verified the conversion. If you are comparing homes, compare the same kind of value for the same assessment period. A difference in terminology is a reason to investigate, not evidence that one assessment is necessarily wrong.

Trace exemptions and other adjustments

Florida’s homestead exemption reduces eligible property’s taxable value. A value reduction belongs in the taxable-value calculation, rather than being subtracted dollar for dollar from the final bill. Official source.

Make separate lines for each exemption or adjustment shown on the notice. Ask whether the adjustment applies to every taxing district or only some of them. If the bill shows different taxable values for different levies, preserve those differences instead of forcing everything into one total. Use the approved exemption for the correct year, and identify any application still pending. If you cannot reconcile a value, request the assessor’s calculation before changing your own payment estimate. Keep an explanation of each adjustment with the bill so next year’s comparison uses the same definitions.

Read the rate and its unit

Florida’s millage guide expresses the tax calculation as taxable value divided by 1,000, multiplied by the millage rate. Always read the unit printed beside a rate before using it. Official source.

For an illustrative taxable value of $200,000 and a hypothetical rate of 15 mills, the calculation is $200,000 ÷ 1,000 × 15 = $3,000. The equivalent percentage in that example is 1.5%. Those are invented inputs for arithmetic practice, not a rate or bill for any county. If the rate is instead stated per $100 of value, use that denominator. Keep the original rate notation beside your converted decimal, then check the result in both forms. Avoid inserting “15” into a percentage calculation when the source says 15 mills.

When several districts levy taxes, calculate each line using its own applicable taxable value and rate, then compare the sum with the bill. Preserve rounding differences for the collector to explain rather than adjusting source figures to make your spreadsheet match. Ask separately about any charge that is not calculated from value and a rate.

Connect the levy to the rate

Illinois explains that tax rates are determined from tax levy ordinances, subject to applicable limits. An assessment is one input; the rates imposed by taxing jurisdictions are another. Official source.

If you want to understand a change, place the previous and current bills side by side. Compare the taxable base, exemption entries, district list and each rate independently. Mark additions or changes that need an explanation. Ask the assessor about valuation and exemption calculations, and ask the appropriate taxing office about the levy or rate. Avoid attributing the whole change to the sale price of your home or to a single official without tracing the figures. For a future budget, show both the assumed value and assumed rate so you can update either input.

Use estimates without confusing them with a bill

Build a simple worksheet with source, period, amount and uncertainty columns. Use official figures whenever available. For a hypothetical scenario, label all inputs “illustration” and keep the result out of your payment calendar until the official bill arrives. If you use the site’s estimate tool, read the explanation of its inputs and limitations before comparing the result with your parcel. Do not use an area-wide comparison as a substitute for the actual levy on your property.

Finish by reconciling the calculated tax with credits, payments and any separately listed charges on the account. Ask the collector for the current balance when payments or corrections have occurred since billing. Save the worksheet as an explanation, while retaining the original bill and payment receipt as the official record. If you identify a specific assessment discrepancy, take the value and supporting evidence to the appropriate review process. If your question is affordability, use the relief and payment resources instead of assuming a mathematical error.

Common questions

Use this guide for your property

• Illinois assessment rules
• Cook County sources
• Estimated property tax tool
• Exemption savings tool
• Appeal preparation

Browse every state or check the national calendar. County pages distinguish announced dates from statutory rules; missing information is labeled.

Sources and verification