On a $400,000 purchase in Ada County, ID, property tax comes to about $1,944 a year — roughly $162 a month — at this county's effective rate of 0.49%.
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Effective rate 0.49% = this county's median owner-occupied tax bill ($2,504, ACS 2022 5-year estimate) divided by the typical home value at the time ($515,628, Zillow, 2022-12-31). Exemptions the seller holds — homestead, senior, veteran — usually do not transfer with the deed, so a new purchase can run above this figure. The county assessor sets the assessed value; this is an estimate, not a quote.
If you pay late
A 2% late charge plus 1% monthly interest applies when the first half is not paid by December 20.
Calendar tax year; bills are issued in November and due December 20, with an optional second half by June 20. If a due date lands on a weekend or public holiday, most counties move it to the next business day — check the county's own notice before relying on the shift.
How to pay
Online: through paydici.com — the only portal this county operates.
By post: mail a cheque to the treasurer's office; the postmark date usually counts, not the arrival date.
In person: the treasurer's office during business hours; bring your bill or parcel number.
Mortgage escrow: if your taxes are escrowed, the servicer pays — you still owe the difference if your escrow is short.
Common questions
When are property taxes due in Ada County, ID?
1st half: December 20, 2026. 2nd half: June 20, 2027.
What happens if I pay late in Ada County?
A 2% late charge plus 1% monthly interest applies when the first half is not paid by December 20.
How do I pay Ada County property tax?
Pay online through paydici.com, the county's own payment portal, or by post or in person at the treasurer's office.
Is the Ada County deadline the same every year?
Calendar tax year; bills are issued in November and due December 20, with an optional second half by June 20. Counties shift dates when billing is delayed, so confirm against the county source linked on this page.
How much is property tax on a $400,000 house in Ada County, ID?
About $1,944 a year, or $162 a month, at this county's effective rate of 0.49%. That rate is the county's median owner-occupied tax bill ($2,504) divided by the typical home value ($515,628). A seller's homestead or senior exemption usually does not transfer, so a new purchase can cost more.
What if I can't pay in full?
Most counties offer instalment plans or partial payment — ask the treasurer before the due date, not after. Once the bill is delinquent the options shrink and the fees start.
Does a late payment affect my mortgage?
Unpaid property tax is a lien on the property in most states, which your servicer may pay and then bill you for, with fees. It does not disappear.
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CountyTaxDates is an independent reference and is not a government agency. Deadlines change and exceptions apply — always confirm with your county treasurer using the official link on this page. Nothing here is tax, legal or financial advice.