How California property tax is calculated: Prop 13, the bills, and the exemptions

How is California property tax actually calculated?

Three parts added together. First, 1% of the assessed value, the base rate set by Article XIII A of the California Constitution. Second, voter-approved bonded debt: a school district building classrooms or a city funding facilities issues bonds, and the repayment lands on the property tax bills in that area. Third, special assessments for things like lighting, refuse and sewer, and in some places Mello-Roos.

So the figure on the bill is usually not 1% but somewhere between 1.1% and 1.3%. It varies noticeably between cities in the same county, so looking at the actual bill for the specific property beats looking at an average.

What is the assessed value, and how does it relate to market value?

The assessed value starts at what you paid for the home. It is reset on a change of ownership or on completion of new construction, and after that it decouples from market value.

That is the heart of Proposition 13. Your neighbour's identical house sells today for $2,000,000 and is assessed there; yours, bought in 2005 for $600,000, is still assessed on that figure grown at a capped rate for twenty years. Two similar homes on the same street with bills that differ threefold is entirely normal in California.

How much can it rise each year?

At most 2%. That is a hard cap: even if market value rises 30% in a year, the assessed value rises 2%.

It does not work symmetrically. When prices fall, the assessed value does not drop automatically; you have to ask for it. See the decline-in-value question below.

Why does an extra bill arrive in the first year after buying?

That is the supplemental bill. When the home changes hands the assessed value moves from the previous owner's figure to your purchase price, and the difference has to be collected from the date of transfer to the end of the fiscal year. That slice is billed separately.

It usually does not go through the lender's impound account and is mailed to the owner instead, so new buyers often assume it is a duplicate and set it aside, then get a late penalty. Expect an extra bill in the year you buy, and do not ignore it.

What is Mello-Roos and how long does it last?

Mello-Roos is a special district formed to fund infrastructure for a particular community, schools, roads, parks, with the cost spread across the owners inside it. It is unrelated to the value of your own home and is most common in newer developments.

It typically runs twenty to forty years and then ends. Within one city, two otherwise similar homes can differ by thousands of dollars a year depending on whether they sit inside a district. Ask specifically whether there is one, how many years remain and how much it is; that money belongs in your monthly budget.

When is it due, and what is the penalty for paying late?

In two installments. The first is due November 1 and becomes delinquent after December 10; the second is due February 1 and becomes delinquent after April 10.

The late penalty is generally 10% of that installment, and other costs can be added.

With a mortgage, most owners have property tax paid from an impound account as part of the monthly payment, but the supplemental bill usually is not included and has to be paid separately.

Which exemptions can be claimed?

The common one is the homeowners' exemption: for the home you occupy as your principal residence, it reduces the assessed value by $7,000. The annual saving is modest, but the form is filed once and keeps applying. It arrives in the mail after you buy, and plenty of people throw it away.

There are also exemptions for seniors, blind and disabled owners and for veterans, each with its own conditions. If you qualify, you have to claim them; the assessor's office will not do it for you.

Prices fell. Can the bill be reduced?

Yes. When a home's market value drops below its assessed value, you can ask the county assessor to assess it temporarily at the lower market value. This is a decline-in-value review, commonly called Proposition 8.

Two things to know. It is temporary: as the market recovers the assessed value follows it back up, to a ceiling of the original base year value grown at the capped rate. And you have to file, within a filing window each year.

Large numbers of California homes went through this after 2008. It is a routine process, not special treatment.

Is property tax deductible against federal income tax?

Yes, up to a limit that has recently changed. Property tax and state income tax are counted together as the SALT deduction.

The 2026 cap is about $40,400, well above the previous $10,000. It phases down for incomes above $500,000, to a floor of $10,000. The increase is temporary: under current law the cap returns to $10,000 in 2030 with no income test.

It only helps if you itemize rather than take the standard deduction. For what you personally can deduct, ask your accountant.

Can the tax base pass to a child with the house?

Since Proposition 19 took effect on February 16, 2021 the rules are tighter: only a family home or family farm qualifies, the child must live there as their principal residence, and the homeowners' exemption must be claimed within a year of the transfer.

Even when it qualifies, the exclusion stops at the original base year value plus $1,044,586, and anything above that is added to the assessed value. The old treatment that also covered other property is gone.

This is worth planning ahead of time.