Property taxes are one of the most important financial considerations in Bay Area real estate, and understanding how they work in Santa Clara County can save buyers from surprises and help sellers position their homes more effectively.
California’s Proposition 13, passed in 1978, caps annual property tax increases at 2% of the assessed value, regardless of how much the market value has appreciated. This means long-time homeowners often pay significantly less in property taxes than recent buyers of comparable homes.
When a property changes ownership, it triggers a reassessment to current market value. For a home purchased at $500,000 twenty years ago that is now worth $4 million, the new buyer’s property tax bill will be based on $4 million, not the previous owner’s assessed value.
For buyers, this means you should always calculate property taxes based on your purchase price, not the current owner’s tax bill. In Santa Clara County, the base property tax rate is approximately 1.2% of assessed value, though the effective rate varies by city and special district assessments. On a $4 million home, expect annual property taxes in the range of $48,000 to $52,000.
A practical example: consider a home in Los Altos purchased in 2000 for $1.2 million. With annual assessed value increases capped at 2%, the 2026 assessed value would be approximately $1.9 million, resulting in annual property taxes around $22,800. If that same home sells today for $4.5 million, the new buyer’s property taxes would be approximately $54,000 per year. The difference, over $30,000 annually, represents a significant ongoing cost.
Supplemental tax bills are another surprise for many first-time Bay Area buyers. When a property is reassessed after a change of ownership, the county issues a supplemental tax bill for the difference between the old and new assessed values, prorated for the remainder of the fiscal year.
Mello-Roos assessments add another layer in some communities. These are not covered by Prop 13’s 2% cap and can add $5,000 to $15,000 or more per year. Always verify whether a property is subject to Mello-Roos before making an offer.
For homeowners considering a move within California, Prop 19’s tax base transfer is one of the most powerful financial tools available. Homeowners over 55 can carry their existing low assessment to a new home, saving tens of thousands of dollars per year.
Ed Graziani helps his clients understand these dynamics as part of every transaction, ensuring they have the full financial picture before buying or selling.
