Can a California assessment appeals board increase my assessed value?

Yes. Per the State Board of Equalization, an appeals board is not bound by the value presented by either you or the assessor, and may leave the value unchanged, decrease it, or increase it.

Is it risky for a homeowner to appeal a decline-in-value assessment?

Usually not very. A Prop 8 appeal asks for a temporary reduction below your factored base year value, so losing generally means the existing base stands rather than a higher assessment. The risk is higher when appealing a base year value after a purchase, or when the assessor's record understates your property.

Will appealing my property taxes cause the assessor to inspect my home?

An appeal is a request to re-examine your property's value, so the assessor may look more closely at their record. If you have unpermitted work or the record understates your square footage or condition, review that before filing.

Does filing an appeal make me a target in future years?

No. There's no mechanism that penalizes filers, and California recomputes your assessed value annually against both the Prop 13 cap and market value regardless. A successful appeal leaves you with a documented valuation baseline that generally helps in later years.

Can Appealing Your Property Taxes Backfire?

You'll find plenty of pages calling a property tax appeal "risk-free." That's not quite true, and the way it's untrue is worth understanding before you file.

The honest answer: yes, the board can raise your value

The State Board of Equalization is explicit about this. An appeals board is not bound by the value presented by you or by the county assessor. It may leave the value the same, decrease it, or increase it.

So the risk is real in the legal sense. The question is when it actually materializes.

Why it rarely happens to homeowners

Three structural reasons:

1. You control the file. For a typical residential decline-in-value appeal, the board is choosing between your comps and the assessor's. An increase requires the assessor to affirmatively argue your property is worth more than they already assessed it at — which means conceding their own roll value was too low. Assessors don't usually walk into a homeowner's Prop 8 hearing planning that.

2. Prop 13 caps the exposure on a regular assessment. Your factored base year value is the ceiling for a Prop 8 appeal. A decline-in-value appeal asks for a temporary reduction below that base; losing means the base stands. It doesn't reset your base year value upward. (How Prop 8 and Prop 13 interact.)

3. The burden may be on the assessor, not you. For an owner-occupied single-family home that qualifies for the homeowners' exemption, §167 puts a rebuttable presumption in your favor. (What that means in practice.)

The realistic downside for most homeowners isn't a higher bill. It's spending a filing fee and an afternoon and ending up exactly where you started.

Where the risk is genuinely higher

Be more careful if:

You're appealing a base year value after a purchase. Here you're arguing the value the assessor set at your change of ownership was wrong. That opens the base year figure itself to scrutiny in both directions. (What appealing a new purchase involves.)
Your property record understates the property. If the assessor's file shows 1,800 sq ft and a permit-scarred remodel actually produced 2,400, an appeal invites someone to look closely at a record that currently favors you. Check what the assessor has on file before you draw attention to it. (How to read your assessment record.)
You have unpermitted work. An appeal is a request for the assessor to re-examine your property. Think through what that examination surfaces.
It's income-producing property. Commercial and rental appeals bring in the income approach, no §167 presumption, and an assessor with more incentive to litigate value.

The two mistakes that create real downside

Filing an unsupported opinion of value. Your application's opinion-of-value figure is effectively a ceiling on your outcome, and a wildly low number costs you credibility with a panel that hears these all day. Ground it in sales before you submit it. (Filling out the application.)

Not showing up. Boards dismiss appeals when applicants don't appear. If you can't make the date, request a postponement — in San Francisco, at least 14 days before the hearing — or send an eligible family member. (The timeline and postponement rules.)

A related worry: does appealing flag you for future scrutiny?

No mechanism exists to punish filers, and in California your assessed value is already recomputed every year against both the Prop 13 cap and current market value regardless of whether you've appealed. What a successful appeal does create is a documented valuation record — which tends to help you next year, not hurt you. (What happens after you win.)

The reasonable way to think about it

Check the assessor's record on your property for anything that understates it. Build a comp set you'd be comfortable defending out loud. If the gap between that and your assessed value is meaningful, file. If it isn't, don't — not because appealing is dangerous, but because you'd be spending a fee and an afternoon to confirm the assessor was right.

CompFinder is a fast way to find out which situation you're in: it pulls comparable sales near the January 1 valuation date for SF, Oakland, San Jose, Seattle, and Issaquah, so you can see the size of the gap before committing to anything.