Think Your San Joaquin County Property Assessment Is Too High? Two Deadlines Give Owners Time to Act
If you own property in San Joaquin County and think the County has assessed it for more than it was actually worth, you still have time to examine the evidence and decide whether to challenge the value.
There are two important deadlines:
- September 15: Request an informal review from the San Joaquin County Assessor.
- November 30: File a regular formal assessment appeal through the San Joaquin County Clerk of the Board.
The difference is straightforward.
An informal review asks the Assessor to take another look at the property’s value.
A formal appeal asks the independent Assessment Appeals Board to decide a disagreement over that value.
Neither process guarantees a reduction.
Before choosing either one, start with the question that matters most:
What was your property actually worth on January 1, 2026?
Start With the January 1 Value
Your assessed value is the value the County Assessor uses for property-tax purposes. It is not necessarily what you could sell your property for today.
For homeowners questioning a decline in value, the important comparison is between the County’s assessed value and the property’s market value on January 1, 2026.
California law allows the Assessor to temporarily reduce an assessment when a property’s market value has fallen below its assessed value.
But falling prices in your neighborhood do not automatically mean your assessment is wrong.
Ask instead:
Was my property’s market value on January 1 lower than its assessed value?
If you think the answer may be yes, look for evidence.
Comparable sales can help.
A comparable property is similar enough to yours to provide useful evidence of what buyers were paying. Location, property type, size, age and condition can all affect whether another property is a meaningful comparison.
The Assessor asks owners seeking an informal decline-in-value review to provide sales that occurred as close to January 1 as possible and no later than March 31.
That means the goal is not to find the lowest-priced properties you can.
The goal is to find properties genuinely comparable to yours that help establish what your property was worth on January 1.
Option 1: Ask the Assessor to Review the Value
If your evidence suggests the assessment may be too high, an informal review may be the simplest place to begin.
San Joaquin County accepts informal requests for review of annual assessments through September 15.
Property owners submit an Informal Request for Decline in Market Value Review to the Assessor’s Office along with evidence supporting the value they believe the property had on January 1.
The Assessor reviews the information and decides whether a change is justified.
If the assessment is changed, the owner receives a Notice of Assessment showing the revised value.
If the Assessor does not change the value—or the owner still disagrees—the informal review does not eliminate the right to pursue a formal assessment appeal.
For questions about the informal decline-in-value review, the Assessor’s Office lists (209) 468-2658. Its general number is (209) 468-2630.
San Joaquin County Assessor’s Office
44 North San Joaquin Street
Second Floor, Suite 230
Stockton, CA 95202
Option 2: File a Formal Appeal
A formal appeal takes the disagreement beyond asking the Assessor to reconsider the value.
The property owner files an Assessment Appeal Application with the Clerk of the Board. If the disagreement is not resolved, the matter may ultimately go before the San Joaquin County Assessment Appeals Board.
For regular 2026 assessments, applications may be filed through 5 p.m. November 30. Mailed applications must be postmarked no later than November 30.
You will need your property’s Assessor’s Parcel Number, or APN. This is the identification number the County uses for your parcel and can be found on assessment notices and property-tax documents.
The application also requires you to state the value currently shown on the assessment roll and what you believe the property is worth.
Do not leave your opinion of value blank. The County’s instructions warn that doing so can cause the application to be rejected.
One application is required for each parcel and each assessment year being challenged.
The County charges a $30 nonrefundable processing fee for each formal application. An exception applies to a single-family, owner-occupied property with an assessed value of $150,000 or less.
Formal applications are submitted to:
Clerk of the Board
44 North San Joaquin Street
Sixth Floor, Suite 627
Stockton, CA 95202
Phone: (209) 468-2350
Keep Paying Your Property-Tax Bill
This point is important:
Filing an appeal does not stop your property-tax bill.
You must continue paying your property taxes by the deadlines shown on the bill while the appeal is pending.
If the Assessment Appeals Board later reduces the assessment, the County says a proportionate refund of taxes already paid will be issued.
Do not withhold a property-tax payment simply because you filed an appeal.
What Happens After You Appeal?
Filing a formal appeal does not necessarily mean you will immediately go to a hearing.
You can continue discussing the assessment with Assessor staff after filing. If you and the Assessor reach an agreement, the dispute may be resolved before the scheduled hearing.
If no agreement is reached, the matter may proceed to the Assessment Appeals Board.
You should be prepared to present evidence supporting the value you are requesting, including relevant comparable sales or other information showing what the property was worth on the date that matters.
The formal application instructs applicants not to attach hearing evidence to the application itself. That evidence is presented later as part of the appeal process.
After considering the evidence, the Board may decrease the assessment, leave it unchanged or increase it.
The County’s instructions state that the Board generally has up to two years after an application is filed to hear the case and make a decision.
Check Your Notice Before Assuming These Deadlines Apply
The September 15 and November 30 deadlines apply to the annual assessment process discussed here.
If you received a different type of assessment notice, your deadline may be different.
For example, a supplemental assessment can follow a change in ownership or new construction. An appeal of a supplemental assessment generally must be filed within 60 days of the mailing date printed on the notice or its postmark date, whichever is later.
Escape assessments and some other assessment changes also have separate filing rules.
If your notice says “supplemental,” “escape assessment,” “roll change” or something similar, do not assume November 30 is your deadline.
Verify the deadline that applies to your specific notice with the County.
Think Your Assessment May Be Too High? Start Here
You do not need to begin by filing anything.
Begin with your documents and the evidence.
- Find your assessed value. Check your assessment notice or property-tax documents.
- Find your APN. You will need it if you pursue a formal appeal.
- Focus on January 1. Ask what your property was actually worth on January 1, 2026.
- Look for credible comparable sales. For an informal review, the Assessor asks for sales as close to January 1 as possible and no later than March 31.
- Decide whether the evidence supports action. Disagreeing with an assessment is not the same as having evidence that it is wrong.
- Watch the deadline that applies to you.
For a regular annual assessment:
September 15 — Informal review deadline
November 30 — Formal appeal deadline
For many homeowners, the informal review may be a reasonable first step because it gives the Assessor an opportunity to examine the evidence before a formal hearing becomes necessary.
But the existence of an appeal process does not mean every property owner should use it.
Do not file simply because a process exists. Do not ignore an assessment simply because challenging it seems complicated.
Know what your property has been assessed at, understand the evidence, know the deadlines and make an informed decision while the opportunity remains open.