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Marin County · San GeronimoSan Geronimo property taxes. A softer market. A higher bill?
In January 2026, the typical home in San Geronimo, in Marin County, was worth about $1,094,000. That's 11.7% below the June 2022 peak of $1,239,000. California assessments don't always fall when the market does, so some San Geronimo owners may be taxed on a value the market no longer supports.
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What San Geronimo home values did
San Geronimo values peaked in June 2022, then slid 11.7% by January 2026, the month that matters for the 2026 assessment. Across Marin County, the typical value was 7.8% below its own peak at the same point, so San Geronimo saw a deeper drop than the county as a whole.
Values have recovered 1.8% since January, through August 2026. That doesn't weaken a 2026 claim, which is judged as of January 1, 2026, but it may narrow any gap on the 2027 roll.
| Measure | Value |
|---|---|
| January 2026 (2026 lien date month) | $1,094,000 |
| Peak since 2021 | $1,239,000 in June 2022 |
| January 2026 vs. peak | -11.7% |
| January 2026 vs. January 2025 | -3.1% |
| Latest (August 2026) | $1,114,000 |
Which San Geronimo owners may be over-assessed
Under Prop 13, your assessment starts at your purchase price and can rise up to 2% a year. Under Prop 8, it must drop to market value whenever market value as of January 1 is lower. The table compares a typical purchase in each year with the January 2026 typical value of $1,094,000.
| Bought in | Typical price that year | Rough 2026 assessment | vs. January 2026 value |
|---|---|---|---|
| 2021 | $1,066,000 | $1,177,000 | Possibly over-assessed by about $82,000 |
| 2022 | $1,180,000 | $1,277,000 | Possibly over-assessed by about $183,000 |
| 2023 | $1,094,000 | $1,161,000 | Possibly over-assessed by about $67,000 |
| 2024 | $1,138,000 | $1,184,000 | Possibly over-assessed by about $89,000 |
| 2025 | $1,102,000 | $1,124,000 | Possibly over-assessed by about $30,000 |
The buyers most likely to be over-assessed are those who bought in 2021, 2022, 2023, 2024 and 2025. A typical 2022 purchase would carry a 2026 assessment of roughly $1,277,000 after the 2% annual increases, about $183,000 more than the January 2026 typical value. At California's 1% base tax rate, that's on the order of $1,830 a year before local voter-approved add-ons.
This is an illustration built on citywide typical values, not an estimate of your home. Your assessment notice shows your actual assessed value, and some assessors lower values on their own in a falling market, so check it first. If you do appeal, your evidence has to show your home's market value.
Marin County deadlines
- 2026 regular filing period: July 2 through November 30, 2026. If you think the 2026 value is too high, this is the window.
- Informal review: the Marin County Assessor may review a decline-in-value request informally. File the formal application anyway if the deadline is close; an informal review doesn't extend it.
- Supplemental or escape assessments: these have their own deadline, generally 60 days from the notice date. Check the notice.
Where San Geronimo owners file
San Geronimo assessments are set by the Marin County Assessor. Formal appeals go to the county's assessment appeals board, not to the city.
| Form | BOE-305-AH, the state Assessment Appeal Application |
|---|---|
| Filing deadline | November 30 (regular window) |
| Where to file | Marin County Clerk of the Board (assessment appeals) |
| Assessor | marincounty.org · 415-473-7215 |
Confirm the current form, fee and address with the county before you file. The Marin County guide lists step-by-step instructions and official links.
Building a San Geronimo case
The numbers above describe the typical San Geronimo home, not yours. Look for sales of similar homes in San Geronimo that closed near January 1, 2026. The BOE treats comparable sales as the strongest evidence for a home, and the appeals board can't consider sales more than 90 days after the valuation date. Match living area, age, condition, lot and location as closely as you can, and write down every difference you can't adjust for.
Smaller communities can have few sales in any month. If nearby San Geronimo sales are thin, widen the search area before you widen the date range, and explain why each sale still compares.
A Vulorean report pulls comparable sales and a January 1 value opinion into one document you can file with. Eligible self-file reports are free during launch, with no payment card required. Review every comparison before you use it; you know your home's condition better than any dataset.
Check your San Geronimo property for free
Start with your address. Eligible self-file reports are free during launch; an account and available report allowance are required. County filing fees are separate.
Start my free property check →Home values: Zillow Home Value Index (ZHVI), all homes, mid-tier, smoothed and seasonally adjusted, through August 2026, from Zillow Research. Purchase-year rows use each year's average typical value and assume the maximum 2% annual increase. Deadlines: California BOE county filing periods. Vulorean is an independent service, not a government office.