Last updated 2026-07-10
TL;DR
San Mateo County's base property tax rate is 1% of assessed value under California's Proposition 13, with local voter-approved bonds pushing the effective rate to roughly 1.10 to 1.20% for most parcels. Tax bills go out around October 1, with installments due November 1 and February 1. Assessment appeals must be filed by November 30 of the assessment year. You can appeal without hiring anyone.
What is the property tax rate in San Mateo County?
San Mateo County's base rate is exactly 1% of assessed value, locked in by California's Proposition 13 (1978). [1] Every parcel then carries a stack of voter-approved debt levies, Mello-Roos charges, and special assessments that vary by city and school district. For most homeowners, the combined effective rate lands between 1.10% and 1.20% of assessed value. Some parcels in newer developments with heavy Mello-Roos bonds run higher. [2]
The County Controller publishes an annual tax rate book that breaks out every levy by Tax Rate Area (TRA). For fiscal year 2023-24, the countywide average effective rate came in around 1.15%, according to that book. [2] Want the exact rate for your parcel? Look up your TRA on the Assessor's parcel tool, then cross-reference it with the tax rate book.
Compare that to la county property tax and santa clara property tax. Same Proposition 13 baseline, different bond portfolios, so effective rates drift by tenths of a percent depending on location. The Prop 13 framework is statewide. Your exact bill is purely local.
How is my assessed value calculated in San Mateo County?
California's Proposition 13 sets your assessed value at the purchase price (the "base year value") and caps annual increases at 2% or the California Consumer Price Index rate, whichever is lower. [1] So a house bought in 2010 for $700,000 can sit at an assessed value well below $1 million today, even after the market value doubled.
The San Mateo County Assessor sets that base year value and applies the inflation factor every January 1. [3] When a property sells, changes ownership, or gets new construction, the Assessor resets the base year value to market value at that event date. Partial transfers, such as adding a co-owner, can trigger partial reassessment depending on who the parties are.
The Assessor can also drop your assessed value below the Prop 13 base if current market value falls beneath it. That's a Proposition 8 reduction. [4] During the 2008 to 2012 housing downturn, San Mateo County reviewed tens of thousands of parcels for Prop 8 relief. Here's the catch. When market values recover, the Assessor restores your value back up to the Prop 13 base plus the accumulated 2% annual bumps. That restoration can spike your assessment in a single year even though the market is only returning to normal.
New construction, including additions, pools, and accessory dwelling units, triggers a partial reassessment limited to the new portion. The rest of the property keeps its existing base year value.
When are San Mateo County property tax bills due?
San Mateo County splits the annual bill into two installments. The first covers July 1 through December 31. It's due November 1 and delinquent after December 10. The second covers January 1 through June 30, due February 1, delinquent after April 10. [5]
Miss December 10 and a 10% penalty hits the first installment automatically. Miss April 10 and you get a 10% penalty plus a $10 cost fee on the second installment. If the bill is still unpaid by June 30, the property goes into tax default and a 1.5% per month redemption penalty starts stacking on top of the original penalty. [5]
Bills mail around October 1 each year. Didn't get yours? You still owe. The San Mateo County Tax Collector posts every bill online. [5] E-check payments are free. Credit card payments carry a processor service fee, not a county charge.
| Installment | Period Covered | Due Date | Delinquent After |
|---|---|---|---|
| First | Jul 1, Dec 31 | November 1 | December 10 |
| Second | Jan 1, Jun 30 | February 1 | April 10 |
If a delinquency date falls on a weekend or county holiday, it moves to the next business day. [5] Worth bookmarking: online tax payment for property covers the mechanics of electronic payments across California counties.
What exemptions can reduce my San Mateo County property tax bill?
California law provides several exemptions that cut your assessed value and, with it, your bill. Most of them require you to file. None are automatic.
Homeowner's Exemption. Own and occupy your home as your principal residence on January 1 and you qualify for a $7,000 reduction in assessed value, worth roughly $70 per year at the 1% base rate. [6] You file once with the Assessor and it renews annually as long as you stay the owner-occupant. New homeowners should file the moment escrow closes so they don't miss the January 1 lien date.
Disabled Veterans' Exemption. Veterans with a 100% service-connected disability rating, or who are blind or have lost two or more limbs, qualify for an exemption of either $100,000 or $150,000 of assessed value depending on income. [6] Surviving spouses of qualifying veterans can claim it too.
Proposition 19 (2021). This replaced the old parent-to-child and grandparent-to-grandchild transfer exclusions. Under Prop 19, a child who inherits a primary residence and uses it as their own primary residence within one year gets a partial exclusion from reassessment, capped at $1 million above the parent's assessed value. [4] Investment properties and vacation homes inherited by children are now fully reassessed at death or transfer.
Prop 19 also expanded over-55 portability. Homeowners 55 or older, severely disabled, or hit by a wildfire or natural disaster can now carry their assessed value to a replacement home anywhere in California, up to three times. [4] Before 2021, this only worked within the same county or between a handful of participating counties. San Mateo was already one of them, but the statewide expansion matters a lot more for owners downsizing across county lines.
Other exemptions include the Welfare Exemption for nonprofits, the Religious Exemption, and the Builder's Exclusion for new construction held for sale. Think one applies? Contact the San Mateo County Assessor directly. Many carry specific filing deadlines.
How do I appeal my San Mateo County assessment?
The formal process runs through the San Mateo County Assessment Appeals Board (AAB), an independent three-member body separate from the Assessor's office. [7] Here's how it works, step by step.
Step 1: Know your deadline. For a regular assessment, the appeal window opens July 2 and closes November 30 of the same assessment year. [7] Miss November 30 and you're locked out until the next cycle, unless a supplemental assessment opens a separate 60-day window. The November 30 deadline is firm. The AAB has no authority to extend it.
Step 2: Request your assessment data. Before you file, call or visit the Assessor and ask for the property record card for your parcel. It shows the characteristics used to calculate your value: square footage, age, condition, and the comparable sales they relied on. Errors here are the single best grounds for a fast reduction.
Step 3: Build your evidence. You need to show the assessed value exceeds fair market value as of January 1 of the assessment year. Two main evidence types: comparable sales (recent sales of similar nearby properties) and an independent appraisal. Comps you pull yourself from public records cost nothing. An appraisal usually runs $400 to $750 for a residential property in San Mateo County, but for a modest over-assessment it may not pencil out. TaxFightBack's DIY appeal kit walks through the exact methodology for pulling and organizing comps, no hired help required.
Step 4: File the application. The Application for Changed Assessment goes to the Clerk of the Board, not the Assessor. [7] File online, in person, or by mail. The residential filing fee is currently $30. [7]
Step 5: The hearing. Most hearings get scheduled within 2 years of filing, though many resolve faster through an informal conference with Assessor staff. Bring your evidence organized and timestamped. The burden is on you to show the value is wrong by a preponderance of the evidence. The panel asks questions and issues a decision, usually within a few weeks of the hearing.
Win, and the Assessor adjusts your roll value while the Tax Collector refunds any overpayment. Prop 13's 2% cap then applies from the corrected base year value going forward, so a successful appeal compounds in your favor every year. [1]
For how the process compares next door, see contra costa county property tax.
What evidence wins a San Mateo County assessment appeal?
The AAB judges fair market value as of January 1 of the assessment year. [7] That date matters. A sale closing in March of the prior year can be more relevant than one closing in February of the current year, depending on how the market moved.
Comparable sales are the backbone of most winning residential appeals. Aim for sales within about a half-mile of your property, within 6 months before or after the January 1 valuation date, with similar square footage, lot size, age, condition, and bed/bath count. Three to five good comps usually does it. San Mateo County's market swings sharply street by street, so geography discipline matters more here than in a flatter market like hennepin county property tax territory.
Got physical problems, damage, or condition issues the Assessor missed? Document them with photos, contractor repair estimates, or inspection reports. Condition adjustments can be persuasive because the Assessor typically values at a standard condition without inspecting every parcel in person.
One thing that never helps: your Zillow estimate. Automated valuation models aren't admissible before the AAB and the panel will set them aside. Use actual recorded sales from the county recorder or a title company data pull.
For income property, the income approach (capitalized net operating income) is standard. San Mateo County commercial owners should pull lease comparables and vacancy data from local brokers, more than sales data, to build a credible income case. See property tax taxation for how the three valuation approaches apply in contested cases.
What is the San Mateo County property tax payment and delinquency process?
Payments go to the San Mateo County Tax Collector. The county takes payment online, by mail, by drop box at the Government Center in Redwood City, or in person. [5] Online e-check is the easiest route and has no service fee.
Pay through a mortgage impound account? Confirm your lender got the bill and paid it before the delinquency dates. Lenders sometimes blow past the December 10 first-installment deadline, and the penalty lands on you as the owner no matter whose fault it is.
Once a property enters tax default (an unpaid balance from a prior fiscal year), the five-year redemption clock starts. If the balance isn't redeemed within five years, the Tax Collector can start a tax sale. The county conducts tax sales when properties reach that stage, though the strong local real estate market means most owners redeem well before then. [5]
Penalty waivers exist, but the bar is high. The Tax Collector can waive penalties only in narrow circumstances, such as a documented casualty loss that directly stopped payment, or a documented county failure to mail the bill to the correct address of record. Forgetting doesn't qualify.
How does San Mateo property tax compare to neighboring counties?
Every California county runs on the same Proposition 13 framework, so the 1% base rate never moves. The variation is all local bond measures that differ by school district, city, and special district boundaries. San Mateo County carries a somewhat heavier bond load than many inland counties, thanks to high-spending K-12 and community college districts plus large infrastructure bond programs.
Here's a rough effective rate comparison. These are approximate figures pulled from each county's published tax rate books. Don't use them for precise planning without verifying your current TRA-specific rate.
| County | Approximate Effective Rate (2023-24) |
|---|---|
| San Mateo | 1.10 to 1.20% |
| Santa Clara | 1.10 to 1.25% |
| San Francisco | 1.15 to 1.20% |
| Contra Costa | 1.10 to 1.30% |
| San Joaquin | 1.05 to 1.15% |
San Joaquin County follows the same Prop 13 base, but its bond overlay is lighter than the Peninsula counties, partly because assessed values are lower and local school bond measures pass at smaller dollar amounts per parcel. The rate gap isn't dramatic. The dollar gap is. On a $1.5 million San Mateo County assessed value versus a $400,000 San Joaquin County value, the actual bills diverge sharply. [2] [8]
For owners with property in multiple Bay Area counties, the appeal processes look structurally similar but deadlines and fee schedules differ. Santa Clara's appeals board uses a slightly different scheduling system than San Mateo's. See santa clara property tax for that county's specifics.
What are the key deadlines San Mateo County property owners must know?
Miss a deadline in California property tax law and it's usually fatal to your options. Here's the full calendar that matters.
| Deadline | What Happens |
|---|---|
| January 1 | Lien date: assessment status and ownership frozen for the tax year |
| February 1 | Second installment due |
| April 10 | Second installment delinquency: 10% penalty + $10 fee |
| July 1 | Assessment appeal window opens for the new assessment year |
| October 1 | Annual tax bills mailed |
| November 1 | First installment due |
| November 30 | Last day to file an Assessment Appeal Application |
| December 10 | First installment delinquency: 10% penalty |
The deadline most homeowners miss is the Homeowner's Exemption window. New owners should file the claim as soon as escrow closes. The exemption pays for the full year only if you file by February 15. File late, by December 10, and you get a partial exemption for the rest of the year. [6]
Prop 19 replacement home claims must be filed within two years of the sale date of the original residence. [4] If you're 55-plus and sold your home, don't wait to file with the Assessor. The clock runs whether or not you knew the exclusion existed.
Supplemental assessments triggered by a change in ownership or new construction open a separate 60-day appeal window from the date the supplemental notice mails. That window is independent of the November 30 regular deadline. [7]
What should I do if I think my assessment has an error?
Start with an informal review request to the Assessor before filing a formal appeal. The San Mateo County Assessor accepts informal reviews, and in clean cases (a data-entry error on square footage, a failure to record a recorded exemption deed) the office can correct the roll without an AAB hearing. [3] This costs nothing and preserves your formal appeal window.
If the informal review doesn't fix it, file the formal Application for Changed Assessment before November 30. Don't wait for the informal process to wrap up if November 30 is close. You can always withdraw the appeal if the Assessor corrects the error first.
Pull your property record card and check every field: square footage, lot size, year built, bedroom and bathroom count, condition classification. Assessors work at scale and errors happen. A 100-square-foot overstatement in living area can add thousands to your assessed value in a market where comparable sales imply $500 or more per square foot.
Taking the DIY route? TaxFightBack's appeal kit gives you a step-by-step framework for organizing evidence and presenting it at a hearing, built for homeowners handling their own cases, and you keep 100% of any refund.
For how appeal outcomes compare across large, expensive markets, nyc property tax and miami dade property taxes show what the process looks like where prices are high and appeals are common.
Can I get a property tax deferral or relief in San Mateo County?
California runs a state Property Tax Postponement program through the State Controller's Office. [9] Homeowners who are 62 or older, blind, or disabled and who meet income and equity requirements can postpone current-year property taxes until they sell the home or transfer ownership. The program charges 7% annual interest (as of 2024) on the deferred amount. [9] San Mateo County properties qualify.
What about a senior exemption at the county level? California doesn't have a blanket county-level property tax break for seniors the way some states do. What California offers instead is Prop 19 portability (carrying your value to a replacement home) and the state postponement program.
Low-income taxpayers in genuine hardship can ask the Tax Collector about payment plan arrangements. These aren't a formal statutory program like the postponement, but the Tax Collector has some discretion to set up installment arrangements on delinquent balances.
One under-used option: if a disaster, calamity, or major damage cut your property's market value after the January 1 lien date, you can file a calamity reassessment claim with the Assessor under Revenue and Taxation Code Section 170. [10] The reduction is usually temporary but can produce a real refund or reduction for the year the damage happened.
Frequently asked questions
What is the exact property tax rate in San Mateo County?
The base rate is 1.00% of assessed value under Proposition 13. Voter-approved bond measures and special assessments add to that, bringing the effective rate to roughly 1.10 to 1.20% for most parcels. Your exact rate depends on your Tax Rate Area. Look up your parcel on the San Mateo County Assessor's website to find your TRA, then check the annual tax rate book published by the County Controller.
When is the San Mateo County property tax appeal deadline?
November 30 of the assessment year is the hard deadline for filing a regular assessment appeal with the Assessment Appeals Board. The window opens July 2. If you receive a supplemental assessment notice, a separate 60-day appeal window opens from the mailing date of that notice, independent of the November 30 deadline. Missing these deadlines typically closes all options for that assessment year.
How do I file an assessment appeal in San Mateo County?
File an Application for Changed Assessment with the Clerk of the Assessment Appeals Board, not the Assessor's office. You can file online, by mail, or in person at the San Mateo County Government Center in Redwood City. The current filing fee is $30 for residential properties. Gather your evidence, including comparable sales or an independent appraisal, before your scheduled hearing.
What is the homeowner's exemption in San Mateo County and how do I apply?
The Homeowner's Exemption reduces your assessed value by $7,000, saving roughly $70 per year at the base rate. You must own and occupy the property as your principal residence on January 1. File the claim with the San Mateo County Assessor. It renews automatically once filed, but new owners should apply as soon as escrow closes to capture the full-year benefit by February 15.
Why did my San Mateo County assessed value jump this year?
Three things cause big jumps: a change in ownership (including some partial transfers) that triggers a full reassessment to market value, new construction completed on the property, or restoration of a prior Prop 8 reduction when market values recover. If none of those apply, the increase should be capped at 2% under Prop 13. Check your assessment notice and contact the Assessor for an explanation if the increase exceeds 2% without a triggering event.
Can seniors transfer their low assessed value to a new home in San Mateo County?
Yes. Under Proposition 19 (effective February 2021), homeowners 55 or older can transfer their existing assessed value to a replacement home anywhere in California, up to three times. The replacement home's value must be equal to or less than the original home's sale price for a full transfer; if it costs more, the difference is added to the carried-over value. File the claim with the Assessor within two years of the sale.
What happens if I miss the December 10 or April 10 payment deadline?
A 10% penalty attaches automatically to whichever installment is late. For the second installment, a $10 cost fee also applies. If the annual bill remains entirely unpaid by June 30, the property enters tax default and a 1.5% per month redemption penalty begins accruing. Penalty waivers are granted only in very narrow circumstances, such as a documented casualty loss that directly prevented payment.
How do I look up my San Mateo County property tax bill online?
Go to the San Mateo County Tax Collector's official website and use the parcel search tool. You can search by address or Assessor Parcel Number (APN). The tool shows current and prior year bills, payment status, and due dates. Online e-check payments are free. Credit card payments carry a processor service fee that the county does not control or retain.
Is San Mateo County property tax higher than San Joaquin County property tax?
The base rate is identical at 1% under Prop 13. San Mateo County's effective rate runs roughly 1.10 to 1.20% versus about 1.05 to 1.15% for most San Joaquin County parcels, reflecting differences in local bond measures. The bigger difference is assessed value: San Mateo County median assessed values are several times higher than San Joaquin County's, so dollar bills are dramatically larger even at similar effective rates.
What is a Prop 8 reduction and should I request one?
A Prop 8 reduction temporarily lowers your assessed value below your Prop 13 base year value when current market value has dropped beneath it. The Assessor reviews parcels proactively in declining markets but you can also request a review. It is worth requesting if your property's current market value is clearly below the assessed value shown on your bill. The reduction reverts as the market recovers, which can cause assessment spikes in later years.
Can I defer San Mateo County property taxes if I am a senior?
California's Property Tax Postponement program lets homeowners who are 62 or older (or blind or disabled) defer current-year taxes until they sell. The program charges annual interest (7% as of 2024) on the deferred amount and requires at least 40% equity in the home. Apply through the California State Controller's Office. San Mateo County properties are eligible as long as the applicant meets the income and equity thresholds.
What evidence does the San Mateo County Appeals Board accept?
The AAB accepts comparable sales of similar nearby properties from around the January 1 valuation date, independent licensed appraisals, inspection reports documenting physical defects, contractor repair estimates, and for income property, rent rolls and vacancy data. Automated valuation model estimates from sites like Zillow are not accepted as evidence. Bring three to five strong comparable sales as your core argument for a residential appeal.
How long does a San Mateo County assessment appeal take?
Most appeals are heard within 12 to 24 months of filing, though straightforward cases often resolve sooner through an informal conference with Assessor staff before the formal hearing. If the Assessor agrees with your evidence during the informal process, the correction can happen without a formal hearing. Once the AAB issues a decision, any refund due is typically processed within 60 to 90 days.
Does refinancing trigger a property tax reassessment in San Mateo County?
No. Refinancing is not a change of ownership under California law and does not trigger a reassessment. Only transfers of a present beneficial interest in the property, meeting the legal definition in Revenue and Taxation Code Section 60, trigger reassessment. Adding or removing a co-borrower on a refinance also generally does not reassess the property as long as the ownership interest itself does not change.
Sources
- California State Board of Equalization, Proposition 13 overview: Proposition 13 caps the base property tax rate at 1% of assessed value and limits annual assessment increases to 2% or the CPI rate, whichever is lower.
- San Mateo County Controller's Office, Annual Tax Rate Book: San Mateo County effective property tax rates by Tax Rate Area, showing the breakdown of base rate plus voter-approved levies for fiscal year 2023-24.
- San Mateo County Assessor-County Clerk-Recorder: The San Mateo County Assessor sets base year values at change of ownership or new construction and applies the annual inflation factor to existing assessments.
- California State Board of Equalization, Proposition 19 information: Proposition 19 (effective February 2021) modified parent-to-child transfer exclusions and expanded the over-55 base year value portability to all California counties, allowing up to three transfers in a lifetime.
- San Mateo County Tax Collector, property tax payment information: San Mateo County property tax first installment is due November 1 (delinquent December 10) and second installment is due February 1 (delinquent April 10), with a 10% penalty on late payments.
- San Mateo County Assessor-County Clerk-Recorder, Exemptions: The Homeowner's Exemption reduces assessed value by $7,000 for owner-occupants; the Disabled Veterans' Exemption provides $100,000 or $150,000 of assessed value reduction depending on income.
- San Mateo County Assessment Appeals Board, Clerk of the Board: Assessment appeal applications must be filed between July 2 and November 30 of the assessment year; the filing fee for residential properties is $30.
- San Joaquin County Assessor, property tax information: San Joaquin County follows California's Proposition 13 base rate structure with local voter-approved levies that generally result in effective rates in the 1.05–1.15% range.
- California State Controller's Office, Property Tax Postponement Program: California's Property Tax Postponement program allows homeowners 62 or older, blind, or disabled who meet income and equity requirements to defer current-year property taxes at 7% annual interest as of 2024.
- California Revenue and Taxation Code Section 170, calamity reassessment: Revenue and Taxation Code Section 170 allows a temporary reassessment reduction for property damaged or destroyed by disaster or calamity after the January 1 lien date.
- California Revenue and Taxation Code Section 60, change of ownership definition: Refinancing does not constitute a change of ownership under Revenue and Taxation Code Section 60 and does not trigger a Proposition 13 reassessment.