Foster City, CA Property Tax: Prop 13, San Mateo County, and the Measure P Levee Tax

Proposition 13, in Plain Terms

California's Proposition 13, approved by voters in 1978, governs every parcel's property tax in the state, Foster City included. A home's assessed value locks in at its purchase price (or the value of completed new construction) at the time of a change of ownership, and can then rise no more than 2% a year regardless of how fast the property's actual market value climbs -- until the next sale resets it. In a market where Foster City's own price trackers already disagree by hundreds of thousands of dollars depending on the source, two similar condos in the same Isle Cove or Shell Cove building can carry meaningfully different tax bills purely because of when each one last changed hands.

The state constitutional base is capped at 1% of assessed value. Actual bills run above that flat 1% almost everywhere in California because of voter-approved local add-ons -- city and county bond measures, school district bonds and parcel taxes, and special-assessment districts -- and which specific add-ons apply to a given Foster City parcel depends on its exact tax rate area within San Mateo County.

San Mateo County Is the Correct Assessor Jurisdiction

Foster City sits entirely within San Mateo County, and the San Mateo County Assessor's Office is the sole, correct jurisdiction for determining assessed value, processing ownership-change reassessments, and administering any Prop 13-related exemptions or exclusions for a Foster City property. There is no separate city-level assessor process -- the City of Foster City's own share of the combined bill (funding city services and, distinctly, the Measure P levee special tax) arrives as line items within the single San Mateo County property tax bill a homeowner receives, rather than through a parallel municipal tax collection process.

Foster City's Effective Rate: A Real, Sourced Number

This page states a real, sourced figure rather than a vague estimate. Ownwell's property-tax data puts Foster City's average effective property tax rate at roughly 1.22%, modestly below the San Mateo County-wide average of roughly 1.25%-1.26%. The same data shows the average Foster City homeowner paying about $9,715 a year in property tax against a county average of $11,405 -- a meaningful gap that likely reflects some combination of Foster City's housing mix (a large share of condominiums and townhomes assessed at lower absolute values than some of the county's larger single-family-home markets) and its specific stack of local add-on levies relative to other San Mateo County cities.

This page did not find a single itemized current list of every voter-approved add-on levy applying to a specific Foster City tax rate area -- San Mateo-Foster City School District's own parcel-tax program is confirmed to exist, but its current per-parcel dollar figure was not independently pulled from a primary source this research pass. Confirm the full current levy stack for a specific parcel with the San Mateo County Tax Collector before budgeting.

The Measure P Levee Special Tax -- a Cost Line Most Markets Don't Carry

Foster City carries a genuinely unusual second tax layer that most other markets on this site do not: a dedicated special tax repaying Measure P, the $90 million general obligation bond Foster City voters approved in June 2018 to fund a FEMA-mandated rebuild of the city's ring levee. Per the city's own levee-project materials, that special tax runs roughly $40 per $100,000 of assessed value annually -- about $560 a year on an average-priced home at the time voters approved it -- for a term described as 30 years. City and levee-project materials pitched that cost explicitly against the alternative: an estimated $2,000 to $3,000-plus a year in mandatory flood insurance premiums indefinitely if the levee had lost FEMA accreditation and the city had been remapped into a mandatory-insurance flood zone.

This page did not confirm the exact calendar year the Measure P special tax is scheduled to sunset for a parcel purchased today, since that depends on the bond's original 2018 issuance date plus its 30-year term -- a buyer should ask the seller's current tax bill or the San Mateo County Tax Collector directly how many years remain on this specific line item before closing, since it is a real, ongoing annual cost distinct from the base Prop 13 rate.

A Worked Dollar Example

Put the sourced figures in real dollars. At a 1.22% base effective rate, a home purchased at $1.6 million (roughly Redfin's trailing 3-month median) would carry a first-year base property tax bill near $19,520. Add the Measure P special tax at roughly $40 per $100,000 of assessed value -- about $640 a year on that same $1.6 million purchase -- for a combined bill near $20,160, before any school district parcel tax or other local add-on is included. These are illustrative, rate-times-price calculations for planning purposes only, not a substitute for the Assessor's own parcel-specific figure.

Because Prop 13 resets assessed value only at a change of ownership, a seller's current tax bill reflects whatever they paid, possibly years or decades ago, and tells a new buyer little about their own future bill. Budget from the actual purchase price times the sourced effective rate above, plus the Measure P special tax, not from whatever figure appears in listing disclosures.

Exemptions and Portability

California's statewide homeowner exemption and transfer rules apply in Foster City the same way they do everywhere else in the state. A modest homeowner's exemption reduces assessed value for an owner-occupied primary residence. Proposition 19 (approved 2020, effective in phases from 2021) lets eligible homeowners age 55 and older, severely disabled homeowners, and wildfire or disaster victims transfer their existing, lower assessed value to a replacement home elsewhere in California -- generally up to three times for age- or disability-based moves -- which can matter for a longtime California homeowner downsizing into a Foster City condo and trying to avoid a full reassessment at current prices. The San Mateo County Assessor's office maintains current forms and eligibility guidance.