Closing calculators
Estimate the property tax credit at a Cook County closing. Because taxes are billed in arrears, the seller credits the buyer for tax that accrued during the seller period but will be billed later. This is a planning tool, not closing advice.
A calculator is a starting point. Get a full picture with a direct review of payoff, taxes, title, condition, and timing.
Enter the last full-year tax bill, the proration percentage your contract uses, and the dates. The accrual start is usually January 1 for a calendar-year proration.
Reviewed and updated June 2026
Cook County collects property tax for a year after that year ends. At closing the seller has lived in the home for part of the current year but the bill has not arrived yet, so the seller credits the buyer for that accrued tax. Contracts often prorate at 100 to 110 percent of the last full-year bill to cushion against increases.
The result is the credit the seller gives the buyer at closing for taxes that accrued during the seller period but are billed later.
| Installment | Amount | Typical timing |
|---|---|---|
| First installment | 55 percent of the prior year bill | Mailed late January, commonly due about April 1 |
| Second installment | Balance after new assessment and rates | Mailed and due in late summer or early fall |
Because the bill arrives after the year it covers, the proration credit at closing keeps each party responsible for taxes during their own period of ownership.
Proration splits the property tax bill between the seller and the buyer based on how much of the period each one owned the home. In Cook County, where taxes are paid in arrears, the seller has not yet received a bill for the current year at closing, so the seller credits the buyer for the tax that accrued from the start of the accrual period to the closing date. The buyer then pays the full bill when it arrives.
The credit is usually figured as a percentage of the last full-year bill. Many contracts use 100 to 110 percent to allow for assessment and rate increases that have not been billed yet. The exact percentage, the accrual start date, and the method are negotiable in the purchase contract, so confirm them with your attorney and title company.
Cook County bills property tax in arrears, meaning the bill for a year arrives after that year. At closing the seller owes tax for the part of the year they owned the home, but the bill has not come yet, so the seller credits the buyer who will pay the full bill later.
Contracts commonly use 100 to 110 percent of the last full-year bill. A higher percentage protects the buyer against assessment and rate increases that are not yet billed. The exact figure is negotiated in the contract.
The first installment, set by law at 55 percent of the prior year bill, is mailed in late January and is commonly due around April 1. The second installment is mailed and due in late summer or early fall once new assessments and rates are set.
No. It is an estimate. The binding proration is calculated by the title company or attorney at closing using the agreed percentage, the exact dates, and the actual bills. Confirm before signing.
Cook County bills property taxes in arrears, meaning the bill arrives after the period it covers. Because the seller owned the home during months that have not been billed yet, the seller credits the buyer at closing so the buyer is not stuck paying the seller's share later.
Yes. The proration is set by the contract, and 100 to 110 percent of the last full-year bill are common. A higher percentage protects the buyer if the next bill rises, while a lower percentage favors the seller, so it is a negotiated term.
This calculator is general information for Chicago-area owners, buyers, and investors. It is not legal, tax, lending, appraisal, or brokerage advice, and rates or rules can change. Verify figures with the appropriate professionals before money moves or documents are signed. Proration terms are negotiated in the purchase contract and finalized by the title company or attorney at closing.