Property Taxes in Half Moon Bay: Prop 13, Explained for a Buyer

Proposition 13, in Practice: Assessed Value Is a Purchase-Date Snapshot

Since California voters passed Proposition 13 in 1978, real property in the state has been assessed at its value at the time of a change in ownership or completion of new construction, with annual increases after that capped at 2% or the rate of inflation, whichever is lower. That means a property's assessed value is essentially frozen near its purchase price and only creeps up slowly year to year -- it does not reset to match rising market prices the way many other states' systems do. When a property sells, the assessed value resets to the new purchase price, and the clock starts over for the new owner.

This single mechanic is why two nearly identical Half Moon Bay homes on the same street can carry meaningfully different property tax bills: one owned by the same family since the 1990s and one that just changed hands. It is also why a buyer cannot simply look up a seller's current tax bill on a listing sheet and assume it will transfer -- it won't. Your own bill will be freshly calculated off your purchase price the year you close.

The Base Rate: 1%, Plus Real Local Additions

California's constitutional base property tax rate under Prop 13 is 1% of assessed value. On top of that base, California law allows voter-approved local bonds and special assessments -- for things like school facility bonds, water district charges, or other local infrastructure -- which push the real, effective rate higher than the bare 1% figure most buyers have heard about. Across San Mateo County, the effective countywide average property tax rate runs roughly 1.26%, with a documented range across different tax rate areas of about 1.08% to 1.52% depending on which specific local bonds and assessments apply to a given parcel.

Ownwell's tracking specifically for Half Moon Bay puts the local median effective rate at around 1.24% -- close to, and consistent with, the countywide average. That means a Half Moon Bay buyer should generally budget somewhere in the 1.1%-1.5% range of their purchase price for the first year's property tax, with the exact figure depending on which of the town's tax rate areas the specific parcel sits in.

What the Assessed-Value Gap Actually Looks Like Here

Ownwell's data shows a median tracked assessed value for Half Moon Bay parcels of $771,902 -- against a current median sale price running roughly $1.5 to $1.7 million across recent market-tracker snapshots. That is not a data error or a stale figure; it is Prop 13 working exactly as designed, keeping longer-tenured owners' tax bills tied to what they originally paid rather than to a market that has since roughly doubled. For a new buyer, the practical implication is direct: your own assessed value -- and your own bill -- will be set at your actual purchase price, not at whatever the town's blended median assessed value happens to be. Don't use a town-wide average assessed value as a proxy for what you personally will owe.

For a concrete illustration: a home purchased today at the roughly $1.7 million median sale price, taxed at an illustrative 1.24% effective rate, would owe approximately $21,080 in the first year ($1,700,000 × 0.0124), calculated here as this page's own arithmetic on two separately sourced figures -- not a quoted bill for any specific property. Get the actual current assessed value and rate for a specific parcel from the San Mateo County Assessor-County Clerk-Recorder before relying on any estimate, including this one.

Reassessment Triggers and What Doesn't Reset the Clock

Because assessed value only resets on a change of ownership or new construction, it's worth knowing in general terms what does and doesn't trigger a reassessment under California law: a standard arm's-length sale does; certain transfers between spouses or, within limits, parents and children, may not, depending on current California law's specific exclusions; and routine maintenance or repairs generally do not count as "new construction" the way a major addition or rebuild would. This page does not state the current, specific eligibility rules or dollar thresholds for California's parent-child transfer exclusion, homeowner's exemption, or any senior/disabled property tax relief program, because rules and thresholds in this area change and a stale number stated here as fact would be worse than no number. Ask the San Mateo County Assessor's office directly about any exemption or exclusion that might apply to a specific transaction.

What a Buyer Should Actually Do

Before making an offer on a Half Moon Bay property, ask the listing agent or title company for the property's current tax rate area code and confirm exactly which local bonds and assessments apply to that specific parcel -- Ownwell's and the county's blended averages are directional, not a substitute for the parcel-specific figure. Ask the San Mateo County Assessor-County Clerk-Recorder directly what your assessed value and first-year tax bill will be based on your actual purchase price, since that is the number that will govern your bill, not the seller's historical one. And if you're relying on any homeowner exemption or transfer exclusion, confirm current eligibility and paperwork requirements directly with the Assessor's office rather than assuming last year's rule still applies.

This page does not state a specific proration formula for a mid-year closing, nor does it state current eligibility thresholds for any California senior citizen, disabled-persons, or base-year-value-transfer property tax relief program -- California does have statewide programs along these lines, but stating stale eligibility numbers as current fact would be worse than not stating them. Ask the Assessor's office directly about any program you might qualify for.