To run an Iowa property tax proration calculator by hand, divide the net annual tax bill by 365 to get a daily rate, then multiply that rate by the number of days the seller owned the property during the current fiscal year (July 1 through the day before closing). That figure is the seller’s share, and it typically shows up as a credit to the buyer on the settlement statement because the buyer will pay the actual bill when it arrives from the county.
The math is simple. The part that trips people up is figuring out which fiscal year you’re prorating, because Iowa taxes run in arrears.
The Fiscal Year You’re Prorating
Iowa’s property tax fiscal year runs July 1 through June 30, and all proration is built around that window.1Iowa Legislature. Iowa Code 441.46 – Assessment Date The full cycle takes roughly eighteen months from assessment to payment. The county assessor sets each parcel’s value on January 1. The taxes tied to that assessment don’t come due until the fall of the following year.2Iowa Department of Revenue. Iowa Property Tax Overview
A concrete example makes it easier. A property assessed on January 1, 2024, generates taxes for the fiscal year running July 1, 2024, through June 30, 2025. The first-half payment on those taxes is due September 30, 2025, and the second half is due March 31, 2026.2Iowa Department of Revenue. Iowa Property Tax Overview By the time the check is written, the period being paid for has already ended. That’s what “taxes in arrears” means in Iowa.
The annual bill is split into two equal installments. The first half must be paid before September 30, and the second half before March 31.3Iowa Legislature. Iowa Code 445.36 – Payment – Installments Miss either date and the unpaid amount becomes delinquent on October 1 or April 1 and starts accruing interest at 1.5 percent per month.4Iowa Legislature. Iowa Code 445.39 – Interest on Delinquent Taxes Any delinquent balance has to be worked into the proration.
What You Need Before You Calculate
Pull these four items together first:
- The closing date from the purchase agreement — the exact day legal ownership transfers.
- The net annual tax amount, meaning the final figure after all credits and exemptions have been subtracted. Your county treasurer’s website shows this on the most recent tax statement.
- The fiscal year the current bill covers. Because of the arrears system, the dates on the bill won’t match the calendar year, so confirm which July 1–June 30 period applies.
- Which installments the seller has already paid, if any.
Use the net amount, not the gross assessment. Credits like the homestead exemption are already baked into the net figure, and using the gross number would overcharge the seller. If you’re not sure which fiscal year a statement covers, the county treasurer can confirm it.
The Formula, Step by Step
Three steps:
- Divide the net annual tax by 365 to get the daily rate.
- Count the days the seller owned the property during the current unpaid fiscal year (July 1 through the day before closing).
- Multiply the daily rate by that day count. The result is the seller’s share.
That amount usually becomes a credit to the buyer at closing, because the buyer will receive and pay the actual tax bill when it arrives. If the seller has already paid an installment before closing, that payment is subtracted from the seller’s obligation, and the seller may end up with a credit back for any overpayment.
A Worked Example
A home closes on October 15, 2025. The net annual property tax for the fiscal year July 1, 2025, through June 30, 2026, is $4,380.
- Daily rate: $4,380 ÷ 365 = $12.00 per day
- Seller’s ownership days: July 1 through October 14 = 106 days
- Seller’s prorated share: 106 × $12.00 = $1,272.00
The buyer receives a $1,272 credit at closing. When the tax bills for this fiscal year arrive (first half due September 30, 2026; second half due March 31, 2027), the buyer pays the full amount but has already been compensated for the seller’s portion. If the seller had paid the first-half installment of $2,190 before closing, that payment would be subtracted from the $1,272 obligation, and the seller would receive a credit for the overpayment instead.
365-Day vs 360-Day Methods
Most Iowa closings use the 365-day (actual calendar year) method shown above. Some settlement agents use a 360-day “banker’s year” method that assumes twelve months of exactly 30 days each. The 360-day version produces a slightly higher daily rate because the same annual amount is divided by fewer days.
On a typical residential bill, the difference is a few dollars. Still, if your own math doesn’t quite match the settlement statement, check which method the closing agent used. Your purchase agreement may specify one; when it doesn’t, the closing agent’s standard practice controls.
Credits That Change the Net Tax
Iowa’s homestead tax credit reduces the taxable value of an owner-occupied primary residence. For assessment years beginning on or after January 1, 2024, the exemption covers $6,500 of taxable value.5Iowa Department of Revenue. Homestead Tax Credit and Exemption The dollar savings depend on the property’s levy rate.6Iowa Legislature. Iowa Code 425.1 – Homestead Credit Fund – Apportionment – Payment For proration purposes, if the seller qualified for the credit, the reduced tax amount carries through to the buyer’s calculation for the rest of the fiscal year. The buyer then needs to file their own homestead application if they’ll use the home as a primary residence.
Iowa also exempts up to $4,000 in taxable value for qualifying veterans with honorable service, for assessment years beginning on or after January 1, 2023.7Iowa Legislature. Iowa Code 426A.11 – Military Service Exemptions Like the homestead credit, this exemption is reflected in the net tax figure and stays attached to the property for the balance of the fiscal year. Confirm any applicable credits appear on the tax bill before running the proration.
Closing Date, Not Possession Date
Iowa tax proration keys off the closing date — the day legal ownership transfers — not the day the buyer moves in.1Iowa Legislature. Iowa Code 441.46 – Assessment Date Those aren’t always the same. Under a rent-back arrangement, the seller stays in the home for an agreed period after closing. The buyer already owns the property from the closing date forward and picks up the tax responsibility from that point, even though the seller is still living there. Any rent-back payment the seller makes to the buyer is separate from the tax proration, which always follows the deed transfer date.
Special Assessments and HOA Dues
Regular property taxes aren’t the only line items divided at closing. Special assessments for infrastructure improvements like street paving, sewer lines, or sidewalks are billed separately and follow their own payment schedule. Iowa’s installment statute explicitly carves out special assessments from the standard September and March timeline.3Iowa Legislature. Iowa Code 445.36 – Payment – Installments Handling depends on the purchase agreement: some contracts require the seller to pay the entire remaining balance, others prorate only the current installment.
Homeowners association dues are prorated the same way as taxes, using a daily rate against the billing period. The seller pays for the days before closing and the buyer covers the rest. Disclose any special assessments or HOA obligations early so the closing agent can pull them into the settlement statement alongside the tax proration.