Skip to content
Free check
Free check

Independent. Not affiliated with any government agency.

Deadlines hub

Property tax appeal deadlines

We track 206 property tax appeal deadlines in 124 counties and cities. The next one closes Oct 5, 2026: King County, WA (Notice mailing group 5), at the King County Board of Appeals and Equalization. Each date links to its official source; forecasts show a labelled range.

Sources: each row's official calendar, rule or notice · Last checked Oct 3, 2026

When is my county's appeal deadline?

Soonest first, grouped by month. Your own assessment notice controls if it prints a different date.

Open now
72
Closing in 30 days
19
Forecasts
98
Download the deadline data (JSON, CSV)All states and counties

Closing soon: the next 14 days

October 2026

November 2026

December 2026

January 2027

March 2027

April 2027

May 2027

June 2027

July 2027

August 2027

September 2027

October 2027

Which counties do you track, and what sets their dates?

Every county we track, by state: the state's rule once verified, the office that hears appeals and each county's official site.

Where do I find my own deadline?

The date that applies to your home is set by your county or state, not by us. These are the places to look.

Your assessment notice

Look for a line such as “last day to file” or “appeal deadline”. If the notice gives a number of days instead, it or the office says which date the count starts from.

The county's official calendar

Some counties set one date for everyone; others open areas or townships on a schedule. Each county above links its official office.

No notice this year?

Ask the assessor’s office which deadline applies to you. Keep a note of who you spoke to and the date they gave.

How do appeal deadlines differ by place?

When are appeals due in the places we track?

  • In Cook County, each township has its own Assessor window, open at least 30 business days after its notices go out, and the Board of Review then opens townships in groups.
  • In King County, a petition is due 60 days after the mailing date printed on your value notice (or July 1, if later), and notices go out one batch of areas at a time.
  • In Philadelphia, market value appeals are due the first Monday of October of the year before the tax year.
  • In the 47 California counties we track, the regular 2026 filing period runs July 2 to November 30, 2026.
  • Outside Cook County in Illinois, a Board of Review complaint is due 30 calendar days after the area's assessment list is published.

Can I download the deadline data?

Yes. The verified windows are open data under CC BY 4.0, with the official sources for each row: deadlines.json and deadlines.csv. About the dataset

Check your home before the deadline

The free check compares your assessment with similar homes and tells you whether it runs in your county.

Check my property

You decide and file yourself.