County filing guide
How to appeal your property tax in Mariposa County
Regular decline-in-value appeals. Supplemental and escape assessments have different deadlines.
Filing options
Filing instructions
Informal review
A short request with the Assessor.
A detailed walkthrough is not available for this filing method.
Formal appeal
The Assessment Appeal Application, filed with the Clerk of the Board.
A detailed walkthrough is not available for this filing method.
After you file
Informal review
Keep your request confirmation and any correspondence from the Assessor. Check the formal appeal deadline above when considering a separate appeal.
Formal appeal
Keep a copy of your application and filing confirmation. Watch for notices from the Clerk of the Board and follow the county’s instructions for any hearing.
Open my appeal plans →Contacts & sources
Clerk of the Board
Runs the formal appeal
209-966-3222 · appeals page ↗
P.O. Box 784, Mariposa, CA 95338
This guide covers the regular decline-in-value appeal; supplemental or escape assessment notices follow different deadlines. Every date and fee here was checked against official sources, listed below with the date checked. If the county's page ever differs from this guide, follow the county's page.
Sources
Informal sources
Informal review
- https://www.mariposacounty.gov/563/Prop-8-Review-Process · “You must file your claim between January 1 and November 30 for the fiscal year beginning on July 1 of that same year.” (checked July 12, 2026)
Formal sources
Formal appeal window
- https://www.boe.ca.gov/proptaxes/pdf/lta26023.pdf · “The regular appeals filing period in each county will begin on July 2, 2026, and will end on September 15, 2026, for those counties where the Assessor mails assessment notices to all taxpayers with property on the secured roll by August 1, 2026. For counties where assessment notices are not mailed by August 1, 2026, the filing period is extended to November 30, 2026.” (checked July 10, 2026)
Filing fee
- https://www.mariposacounty.gov/120/Assessment-Appeals · “As of 2024, all applications will require a non-refundable $30 filing fee, per resolution 2024-237.” (checked July 12, 2026)
Filing address
- https://www.mariposacounty.gov/120/Assessment-Appeals · “Complete the necessary form and mail to: Clerk of the Board of Supervisors P.O. Box 784 Mariposa, CA 95338” (checked July 12, 2026)
Common questions about appealing in Mariposa County
When is the deadline to appeal in Mariposa County?
The deadline to file a formal appeal in Mariposa County for the 2026-27 tax year is November 30, 2026. Filing opened July 2, 2026.
The Assessor takes informal review requests from January 1 to November 30, 2026.
What does it cost to file an appeal in Mariposa County?
The county filing fee for a formal appeal is $30.
Informal review or formal appeal: which one first?
Mariposa County offers both: an informal review with the Assessor, and a formal appeal filed with the Clerk of the Board (due November 30, 2026).
The state's own guidance says to talk to the Assessor's office first: if their staff finds an error, they can lower the roll directly and you may never need to file. Missing an informal review costs you nothing; missing the formal deadline costs you the year.
Which form do I file, and where?
We have not established which application form Mariposa County requires.
The Clerk of the Board's address is P.O. Box 784, Mariposa, CA 95338.
Check the Clerk of the Board's appeals page ↗ or call 209-966-3222 before you file.
How long does an appeal take?
You get written notice at least 45 days ahead, hearings are open to the public (you can watch one first), and boards are expected to decide within two years of filing. You can still settle at any point before your date.
Do homeowners actually get their assessments lowered?
More than 150,000 homes across California had temporarily reduced assessments in tax year 2025-26.
How appeals work in California
There are two tracks, and they are not the same thing
The informal review is a conversation with the County Assessor: optional, non-binding, and often enough to fix an inflated value. The formal appeal is a filed application to an independent appeals board. Only the formal filing preserves your legal rights for the year.
The formal filing is what protects you
An informal request, an email thread, or a pending conversation preserves nothing. If the filing window closes while you wait for an answer, the year is gone. When in doubt, file the formal appeal and keep talking.
Most appeals end in an agreement, not a hearing
You and the Assessor can agree on a value any time before the hearing. The agreement is written and signed (a "stipulation") and goes to the board for approval, and the hearing is canceled.
Your evidence is comparable sales, and the law sets a cutoff
Boards decide on sales of homes similar to yours. By law, a sale that closed more than 90 days after the valuation date (January 1 for a decline-in-value appeal) cannot be admitted as evidence; submitting later sales is the most common mistake applicants make.
For your own home, the Assessor has to prove their number
For an owner-occupied single-family home, the burden of proof at the hearing is on the Assessor, who must present evidence first. You still need your own evidence, but the default favors you.
The board rules on evidence, and can move the value either way
An appeals board can lower, confirm, or raise an assessed value based on what is presented. That is why the appeal rests on comparable sales, not on how the tax feels.
Keep paying, and check again every year
Property taxes stay due while an appeal is pending; a win comes back as a refund with interest. A decline-in-value reduction applies to the year you filed for, so check your new assessed value each year and appeal again if it is still high.