About this tool
Property Tax Proration Calculator is a free, in-browser tool that divides a year's property tax between the buyer and seller based on how many days of the tax year each one owns the home. Enter the annual tax, the closing date and the proration convention, and it shows each party's share. All math runs locally on your device.
The daily tax rate is the annual tax divided by 365. The seller's days of ownership are counted from January 1 to the closing date using UTC-based date arithmetic (Date.UTC), which is immune to daylight-saving and timezone shifts. Under the most common convention the closing day belongs to the buyer, so the seller owns Jan 1 through the day before; the alternate convention gives the closing day to the seller. The seller's share is daily rate × seller days, and the buyer's share is the annual tax minus the seller's share.
Use it to check the proration line on a settlement statement. Conventions genuinely vary by locale and contract — whether the closing day counts to the buyer or seller, and whether taxes are billed in arrears or advance — so pick the method your closing uses and treat the result as an estimate.
Frequently asked questions
How are the days of ownership counted?
From January 1 of the tax year to the closing date, using UTC millisecond math (Date.UTC) so the count is DST- and timezone-safe. The two method options decide whether the closing day itself is charged to the buyer (most common) or to the seller.
Why divide by 365 instead of the actual days in the year?
A flat 365-day basis is the most widely used proration convention and keeps the daily rate stable. The tool clamps the seller's days to 365 so the buyer's share is never negative, even on a leap-year closing.
What does 'seller pays through day before closing' mean?
It is the common US convention where the seller is responsible for taxes up to but not including the closing day, and the buyer owns the property from the closing day onward. The alternate option assigns the closing day to the seller instead.
Does the split depend on my local rules?
Yes — proration customs differ by state and country, including arrears versus advance billing and how the closing day is counted. This tool computes a clean day-based split from the values you enter; confirm the exact convention with your closing agent. Everything runs in your browser.
More tools