San Mateo County Rent Control: AB 1482 Cap, Exemptions, and Just Cause

Rent control in San Mateo County runs mostly on state law. California’s Tenant Protection Act caps annual rent increases at 5% plus the regional change in the Consumer Price Index, and from August 1, 2025 through July 31, 2026 that works out to 6.3% for units in the county.¹ East Palo Alto is the only city in the county with its own stricter ordinance for standard residential rentals. Whether any of this reaches your unit depends on the building’s age, who owns it, and where in the county it sits.

The Statewide Cap and the Current Number

Civil Code Section 1947.12, part of the Tenant Protection Act of 2019 (AB 1482), is the baseline for the whole county. Your landlord cannot raise rent by more than 5% plus the regional CPI change over any 12-month period, and the total is hard-capped at 10% no matter how high inflation runs.² The increase is measured against the lowest rent charged for the unit during the prior 12 months, so a landlord cannot temporarily drop rent and then reset a higher ceiling.

San Mateo County sits in the San Francisco-Oakland-Hayward CPI region. The Attorney General set the maximum allowable increase at 6.3% for the period running August 1, 2025 through July 31, 2026, reflecting 1.3% CPI growth during the measurement window.¹ The cap recalculates every August based on the April-to-April CPI change. The statewide framework governs unincorporated areas and every incorporated city in the county except where a local rule is stricter. The rent cap is set to sunset on January 1, 2030 unless the legislature extends it.

Notice Your Landlord Must Give

Even a legal increase is not enforceable until proper notice has been served under Civil Code Section 827:

30 days’ notice when the cumulative increase over the prior 12 months is 10% or less of the rent at the start of that period.
90 days’ notice when the cumulative increase exceeds 10% over any 12-month window.

The clock starts on delivery, not the date on the paper. First-class mail adds five days.³ If a new amount takes effect before the notice period expires, you do not owe it yet.

East Palo Alto’s Stricter Local Rules

East Palo Alto is the one city in the county running full rent stabilization for standard residential units. Voters adopted the current Rent Stabilization and Just Cause for Eviction Ordinance in 2010, and a Rent Stabilization Board oversees adjustments, complaints, and rent registration.⁴

The allowed annual increase is tied to 80% of the CPI change, capped at 10%, and the current figure is 2.2%.⁵ A landlord who wants more must petition the Rent Board and show a specific financial justification.⁶ Because the local formula produces a smaller increase than the state’s, it takes precedence for covered units in East Palo Alto; state law explicitly steps aside when a local ordinance is stricter.²

Brisbane, Pacifica, and unincorporated San Mateo County run rent stabilization programs too, but only for mobile home parks. If you rent a house or apartment in those places, state law is what applies to you.

Units That Are Exempt

Plenty of rentals in the county fall outside rent control. The main exemptions:

Buildings Under 15 Years Old

Any unit whose certificate of occupancy is less than 15 years old is exempt from the statewide cap.² Under Costa-Hawkins, any unit with a certificate of occupancy issued after February 1, 1995 is also permanently exempt from local rent control. A building finished in 2015 sits outside the statewide cap until 2030 but is already outside East Palo Alto’s local ordinance for good.

Single-Family Homes and Condominiums

Single-family homes and condos are generally exempt from the statewide cap, but only when the owner is not a corporation, a REIT, or an LLC with a corporate member.² The exemption also requires a specific written disclosure to the tenant citing Sections 1947.12 and 1946.2. Without that disclosure, the cap applies by default.

Owner-Occupied Duplexes

If you own a duplex and live in one of the two units as your principal residence, the other unit is exempt from the statewide cap. The exemption lasts only while you live there and does not apply if either unit is an ADU or junior ADU.²

Mobile Homes

Mobile homes are treated separately. They are not exempt from the statewide cap on the basis of building age the way other housing types are, and the Mobilehome Residency Law adds its own layer for park spaces.

Vacancy Decontrol Between Tenancies

Under the Costa-Hawkins Rental Housing Act, a landlord can reset rent to market when a unit turns over. This applies even in East Palo Alto. The controlled rent your neighbor pays after ten years does not set your starting rent when you move in. Once the prior tenant leaves or the tenancy is lawfully terminated, the landlord sets a new initial rate, and the annual cap then runs from that number for the length of your tenancy.

Just Cause Eviction and Relocation Payments

After 12 months of continuous occupancy, your landlord needs a legally recognized reason to end your tenancy. Civil Code Section 1946.2 applies whether or not your unit is under the rent cap.⁷

At-fault reasons include nonpayment of rent, a material lease violation after a written warning, and nuisance. No relocation payment is owed for at-fault evictions.⁷

No-fault reasons include the landlord or a close family member moving in, or the landlord withdrawing the property from the rental market under the Ellis Act. In these cases, the landlord owes relocation assistance equal to one month of the rent that was in effect when the termination notice was served, paid within 15 calendar days of the notice or waived in writing as the tenant’s final month of rent.⁷ Failure to follow the relocation requirements exactly voids the termination notice. A no-fault notice that doesn’t state your relocation right or specify the waived amount may be defective.

Security Deposit Cap

Under Civil Code Section 1950.5, as amended by AB 12 in 2024, most landlords can charge a maximum security deposit of one month’s rent, furnished or unfurnished. A small-landlord exception allows up to two months’ rent if the owner is a natural person (not a corporation or an LLC with a corporate member) and owns no more than two rental properties totaling four or fewer units. Even then, if the tenant is an active-duty service member, the cap stays at one month’s rent.⁸

After you move out, the landlord has 21 days to return the deposit with an itemized statement of any deductions. If repairs run longer than 21 days, the landlord must send a good-faith estimate and then a final accounting with the remaining balance within 14 days of finishing the work.

Where to Get Help

Tenants in unincorporated areas can file complaints with the county housing program; residents of incorporated cities should contact local code enforcement.⁹ East Palo Alto tenants can bring disputes to the Rent Stabilization Board rather than going straight to court.

For free legal advice, the county directs tenants to the Legal Aid Society of San Mateo County at 650-517-8911, Monday through Friday, 9 a.m. to 5 p.m., and to Community Legal Services in East Palo Alto.¹⁰ Getting guidance before you respond to a rent increase notice or an eviction filing is often what determines the outcome.

1
California Attorney General. Know Your Rights as a California Tenant
2
California Legislative Information. California Civil Code 1947.12 – Limitation on Rent Increases
3
California Legislative Information. California Civil Code 827
4
City of East Palo Alto. Rent Stabilization Program
5
California Attorney General. Local Rent Stabilization Laws – Permissible Rent Increases
6
City of East Palo Alto. Rent Stabilization Board
7
California Legislative Information. California Civil Code 1946.2 – Tenancy Termination
8
California Legislative Information. California Civil Code 1950.5
9
San Mateo County Health. Housing Program
10
County of San Mateo, CA. Tenants Protections and Rights