Home › Guides › California cities › Union City
Alameda County · Union CityUnion City property taxes. Below the peak. Is your bill?
In January 2026, the typical home in Union City, in Alameda County, was worth about $1,223,000. That's 6.2% below the May 2022 peak of $1,304,000. California assessments don't always fall when the market does, so some Union City owners may be taxed on a value the market no longer supports.
Check my Union City property for free →
What Union City home values did
Union City values peaked in May 2022, then slid 6.2% by January 2026, the month that matters for the 2026 assessment. Across Alameda County, the typical value was 10.6% below its own peak at the same point, so Union City saw a smaller drop than the county as a whole.
Values kept falling after January: by August 2026 the typical home was 2.0% lower again. If that holds through January 1, 2027, next year's case could be stronger than this year's.
| Measure | Value |
|---|---|
| January 2026 (2026 lien date month) | $1,223,000 |
| Peak since 2021 | $1,304,000 in May 2022 |
| January 2026 vs. peak | -6.2% |
| January 2026 vs. January 2025 | -5.9% |
| Latest (August 2026) | $1,199,000 |
Which Union City 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 $1,223,000.
| Bought in | Typical price that year | Rough 2026 assessment | vs. January 2026 value |
|---|---|---|---|
| 2021 | $1,060,000 | $1,170,000 | Below market |
| 2022 | $1,224,000 | $1,324,000 | Possibly over-assessed by about $101,000 |
| 2023 | $1,152,000 | $1,223,000 | Below market |
| 2024 | $1,272,000 | $1,324,000 | Possibly over-assessed by about $100,000 |
| 2025 | $1,260,000 | $1,285,000 | Possibly over-assessed by about $62,000 |
The buyers most likely to be over-assessed are those who bought in 2022, 2024 and 2025. A typical 2022 purchase would carry a 2026 assessment of roughly $1,324,000 after the 2% annual increases, about $101,000 more than the January 2026 typical value. At California's 1% base tax rate, that's on the order of $1,010 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.
Alameda County deadlines
- 2026 regular filing period: closed September 15, 2026. Alameda County uses the earlier California window.
- Next regular filing period: July 2 through September 15, 2027, for the 2027 roll.
- Before then: ask the Alameda County Assessor how and when it accepts informal decline-in-value review requests for 2027. An informal review never extends the formal deadline.
- Supplemental or escape assessments: these have their own deadline, generally 60 days from the notice date. Check the notice.
Where Union City owners file
Union City assessments are set by the Alameda 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 | September 15 (regular window) |
| Where to file | Alameda County Clerk of the Board (assessment appeals) |
| Appeals office | acgov.org |
| Assessor | acassessor.org · 510-272-3787 |
Confirm the current form, fee and address with the county before you file. The Alameda County guide lists step-by-step instructions and official links.
Building a Union City case
Market averages explain why an appeal might work. The board decides on evidence about one property. Look for sales of similar homes in Union City 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.
Union City sits in the San Francisco-Oakland-Berkeley metro, but neighborhood differences matter more than metro trends. A sale across town can be a weaker comparison than one a few streets away.
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 Union City 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.