Prop 19 for San Mateo home sellers

Updated September 17, 2026. General information for sellers in the city of San Mateo, California. It is not legal or tax advice.

California's property tax is based on a home's assessed value, which usually rises slowly while you own it. Many long-time San Mateo owners pay tax on a value far below today's market. Proposition 19, approved by voters in 2020, changed two rules that matter to them. One lets some owners take their lower tax base with them when they move. The other limits what children can keep when they inherit a home.

Moving and keeping your tax base

According to the California State Board of Equalization (BOE), Prop 19 lets eligible homeowners transfer the taxable value of their primary home to a replacement home. Since April 1, 2021, you may qualify if you are:

age 55 or older,
severely and permanently disabled, or
a homeowner whose home was substantially damaged by a wildfire or natural disaster.

You only need to meet one of these. The replacement home can be anywhere in California. Owners who are 55 or older, or disabled, can use the transfer up to three times.

How the value rules work

The BOE explains the value test this way. If the replacement home is of equal or lesser value than the market value of the home you sold, your old taxable value moves over without an increase. "Equal or lesser" depends on timing:

100% of the old home's sale value, if you buy the replacement before you sell,
105%, if you buy it within the first year after the sale,
110%, if you buy it within the second year after the sale.

If the replacement costs more than that, the difference is added to the taxable value you transfer. You can still use the benefit on a more expensive home, but your tax base will be higher.

The home you sell must be your principal residence, eligible for the homeowners' exemption, either when you sell it or within two years of buying the replacement. The replacement must be bought or built within two years of the sale. You claim the transfer with BOE form 19-B, filed with the county assessor within three years of buying the replacement. In San Mateo County, that is the Assessor-County Clerk-Recorder.

What changed for parents and children

Before Prop 19, parents could pass a home to their children without a reassessment, whatever its value. Since February 16, 2021, the BOE says the exclusion applies only to:

a family home that was the parent's principal residence and becomes the child's principal residence, or
a family farm.

The child must claim the homeowners' exemption within one year of the transfer. A home the child rents out does not qualify. There is also a value limit. The excluded amount is the home's taxable value plus $1 million, adjusted every two years. For transfers from February 16, 2025 through February 15, 2027, the BOE set the adjusted amount at $1,044,586. If the home's market value is above the limit, the difference is added to the taxable value.

An example from the BOE

The BOE's Prop 19 fact sheet gives this example, using the unadjusted $1 million figure. A family home has a taxable value of $300,000 and a market value of $1,500,000. The limit is $300,000 plus $1,000,000, or $1,300,000. The market value is $200,000 over that, so $200,000 is added. The child's new taxable value is $500,000.

Why this matters when you are deciding to sell

Downsizing after 55. If you have owned your San Mateo home for a long time, Prop 19 may let you move to a smaller or cheaper home without a big jump in property tax.
Inherited homes. If no heir will live in the home, it is reassessed at market value when it passes to them. Many families then decide to sell. See our guide to selling an inherited home.
Timing. Deadlines run from the dates of sale and purchase, so plan both moves together.

Prop 19 has more detail than fits here. Before you sell or transfer a home, read the BOE's pages and ask the San Mateo County Assessor how the rules apply to you.

Thinking about selling? Ask for a free home value estimate. A licensed San Mateo agent replies by email, and there is no obligation.

Sources

Laws and amounts change. Check the sources above, and talk to an attorney or tax advisor about your own situation.