San Francisco county property tax is about 1.18% of your home's assessed value for fiscal year 2025-26 (SF Treasurer), and that assessed value is set to your purchase price when you buy. Proposition 13 then caps how fast it climbs. Supplemental bills, Mello-Roos, and appeals all build on that base.
Unless otherwise noted, all market figures in this guide are from MLS data.
Most of the buyers I work with come into a purchase with a rough number in their head for property tax, usually "about 1% of the price," and then get surprised twice: once when the composite rate lands closer to 1.18%, and again a few months after closing when a second bill they did not budget for shows up in the mail. Neither surprise is exotic. Both fall directly out of how California and San Francisco assess property. The part that trips people up is not the rate itself. It is the timing, the reassessment on sale, and the handful of districts that carry an extra special tax on top of the standard rate. I'm Chris Chour, founder and broker of EON Real Estate, and most of my work is single-family and condo transactions in San Francisco's luxury neighborhoods, where the year-one tax math is often the difference between an offer that pencils and one that does not. Get the mechanic right before you write the offer, not after the first bill lands.
How San Francisco property tax is actually calculated
The foundation is Proposition 13, passed by California voters in 1978 and written into the state constitution as Article XIII A (California State Board of Equalization). It fixes the base property tax rate at 1% of a property's assessed value. San Francisco's total secured rate runs slightly higher, approximately 1.18% for fiscal year 2025-26, because voter-approved bond measures (for schools, transit, and city infrastructure) are added on top of the 1% base and repaid through your tax bill (SF Treasurer & Tax Collector).
Two numbers drive the bill: the rate and the assessed value. Prop 13 governs both. The assessed value is not your home's live market value. It is a base-year value, set at your purchase price when ownership changes, that can then rise by at most 2% per year regardless of how fast the market moves (California State Board of Equalization). That 2% cap is the reason a longtime owner two doors down can pay a fraction of what a new buyer pays for a nearly identical house. Their base-year value was locked in years ago and has crept up slowly; yours resets to today's price.
The tax funds local government, and the "secured" label just means the tax is secured by the real property itself: the land plus the buildings and fixtures that convey with it, what real estate calls appurtenances. Personal property like vehicles is taxed separately and is not part of the secured bill on your home.
The parts that catch buyers: a decision tree
Reassessment on sale
A change of ownership establishes a new base-year value equal to your purchase price (SF Office of the Assessor-Recorder). This is why a new owner's bill is almost always higher than the seller's was. The reassessment is triggered by the recorded sale, not by an inspector walking through, so it happens automatically once the deed records.
New construction
Adding square footage, a unit, or the equivalent triggers a reassessment of the new work (SF Office of the Assessor-Recorder). Routine maintenance and repairs do not. Absent a sale or new construction, your assessed value simply drifts up at the 2% annual cap.
The supplemental bill
After you buy, the Assessor issues a supplemental assessment for the difference between the prior owner's assessed value and your new purchase-price base, prorated for the months left in the fiscal year (SF Office of the Assessor-Recorder). A supplemental assessment is simply the catch-up charge that covers the gap between the old low assessment and your new one. It arrives separately from, and on top of, the regular annual bill, and it is the single most common "wait, what is this?" question buyers raise after closing.
Mello-Roos and special districts
Some parcels sit inside a Community Facilities District, known as Mello-Roos after the 1982 state act that created them, and carry an additional special tax to fund local public facilities (SF.gov Special Tax District Reports). In San Francisco these cluster in newer master-planned areas: CFD 2014-1 (Transbay), CFD 2016-1 (Treasure Island), STD 2020-1 (Mission Rock), and the OCII districts covering Mission Bay and Hunters Point Shipyard/Candlestick. If you are still learning the SF neighborhood map, those are the pockets to watch. The special tax shows up as a line item on the secured bill, so two otherwise similar condos can carry very different total taxes if one is inside a district and the other is not. Always read the actual bill.
What this looks like in practice
Run the math on a purchase at San Francisco's median closed price, which was $1.766M over the trailing 12 months, with an average of $1,198 per square foot (MLS). When you close, that $1,766,000 becomes your base-year value. The 1% Prop 13 base alone is $17,660. At the roughly 1.18% composite rate, the full first-year annual bill is approximately $20,839, with about $3,179 of that being the voter-approved bond add-ons layered on top of the base (SF Treasurer & Tax Collector).
That is the regular bill. On top of it, the supplemental bill covers the jump from the seller's old assessed value to your $1,766,000, prorated from your purchase date to the end of the fiscal year on June 30 (SF Assessor). If the seller was a longtime owner with a low Prop 13 base, that gap is large, and the supplemental can run into five figures. Budget for it as a separate line, because it is not folded into your monthly mortgage impound at closing.
Year two is where the 2% cap earns its keep. Your assessed value can rise to at most $1,801,320 (a 2% step up), so the annual bill nudges to roughly $21,256 even if the market runs far hotter than 2% (California State Board of Equalization). When I run the year-one numbers for a buyer, both bills, the annual and the supplemental, go on the table before we write.
San Francisco property tax by the numbers
What to consider before you write the offer
I don't sugarcoat the supplemental bill, because it is where most first-year budgets break. Three tradeoffs come up again and again.
The rate is not a flat 1%
The Prop 13 base is 1%, but San Francisco's composite secured rate is approximately 1.18% for 2025-26 once voter-approved bonds are added (SF Treasurer & Tax Collector). On a $1.766M purchase that difference is more than $3,000 a year, so budgeting at a flat 1% understates the real number.
The supplemental bill is a separate mailing
It is prorated and not folded into your closing impound (SF Assessor). Buyers who plan only for the regular annual bill get caught short a few months in, especially when the seller was a longtime owner and the assessed-value jump is large.
Missing a delinquency date costs 10%
The secured tax is paid in two installments. Miss either delinquency date and a 10% penalty attaches to that installment immediately, with more cost if it stays unpaid (SF Treasurer & Tax Collector).
One more, less a tradeoff than a missed opportunity: if your home's market value falls below its assessed value, you are not stuck. Proposition 8 (also 1978) requires the Assessor to enroll the lower of your Prop 13 base or current market value as of the January 1 lien date, so you can request a decline-in-value review to bring the bill down until values recover (SF Office of the Assessor-Recorder).
What is the property tax rate in San Francisco?
As of fiscal year 2025-26, San Francisco's total secured property tax rate is approximately 1.18% of assessed value (SF Treasurer & Tax Collector). That is the 1% Proposition 13 base plus voter-approved bond debt service for schools, transit, and infrastructure. The exact composite rate is set annually and runs just over 1%, so budget above a flat 1% when you estimate a purchase.
How is my property tax bill calculated when I buy a home in San Francisco?
When you buy in 2026, your assessed value resets to your purchase price, and the first-year annual bill is roughly 1.18% of that figure (SF Assessor; SF Treasurer & Tax Collector). On San Francisco's $1.766M median closed price, that is about $20,839 a year (MLS). A separate supplemental bill then covers the gap between the seller's old assessment and yours.
What is a supplemental property tax bill?
As of 2026, a supplemental property tax bill is a one-time charge for the difference between the prior owner's assessed value and your purchase-price base, prorated from your purchase date through June 30 (SF Office of the Assessor-Recorder). It arrives separately from, and on top of, the regular annual bill, usually a few months after closing, and it is not included in your closing impound.
Can I lower my San Francisco property tax assessment?
Yes, and as of 2026 you can either request a Proposition 8 decline-in-value review if your market value has dropped below your assessed value, or file a formal appeal with the SF Assessment Appeals Board between July 2 and September 15 (SF Office of the Assessor-Recorder; SF Assessment Appeals Board). Appeals are won on evidence: comparable sales near the January 1 lien date that support a lower value.
When are San Francisco property taxes due?
For fiscal year 2025-26, the first installment is due November 1 and delinquent after December 10, and the second installment is due February 1 and delinquent after April 10 (SF Treasurer & Tax Collector). The first installment covers July 1 through December 31; the second covers January 1 through June 30. Miss a delinquency date and a 10% penalty attaches.
Does Proposition 19 let me keep my low tax base if I move?
Yes, and as of 2026 Proposition 19 (effective April 1, 2021) lets homeowners who are 55 or older, severely and permanently disabled, or victims of a wildfire or declared disaster transfer their base-year value to a replacement home anywhere in California, up to three times (California State Board of Equalization). Buy equal or lesser value and the base transfers unchanged; buy up and the difference is added on.
Why an assessment appeal is where a broker earns the fee
An appeal is decided on market-value evidence: comparable sales of similar nearby homes around the January 1 lien date that show your assessed value overstates what the home would actually sell for (SF Assessment Appeals Board). That comp set is exactly the work I do to price a listing or an offer, so assembling it for an appeal is a natural extension. EON is a member of Top Agent Network, an invite-only group for the top 1% of agents by production, which is the same market read that backs a credible appeal. It is also a reason owners stay in touch with an agent year to year, not just at the closing table.
Talk to me about property tax
If you are weighing an offer and want the real year-one number, both the annual bill and the supplemental, or you think your current assessment is too high and want to know whether the comps support an appeal, I can pull the numbers and walk you through them. No pressure, just the math you need before you decide.
