A California property tax assessment is set at your home’s purchase price, climbs no more than 2% a year while you own it, and only resets to current market value when the property changes hands or you add new construction. That assessed value, called the Base Year Value, is multiplied by a base tax rate capped at 1% to produce your bill, with voter-approved bonds added on top. The system comes from Proposition 13, and it is the reason two identical houses on the same street can carry very different tax bills depending on when each owner bought.
How Your Base Year Value Is Set and Adjusted
Every calculation starts with the Base Year Value: the fair market value of your property on the date you bought it, or for new construction, the date the work was completed. In a normal arm’s-length purchase, that figure is just the price on the deed. The county assessor records it and uses it as the foundation of your tax bill for as long as you own the property.
Each year, the assessor adjusts that number upward by the change in the California Consumer Price Index, but the increase can never exceed 2%. The assessor applies whichever is lower, the actual CCPI change or the 2% ceiling.1California State Board of Equalization. 2024-25 California Consumer Price Index Letter to County Assessors The resulting number is called the Factored Base Year Value, and it is the maximum the assessor can use to calculate your taxes in any given year.
The cap kicks in frequently. For the 2025–26 assessment year, the CCPI change came in above 2%, so assessors applied the 2% maximum instead.2California State Board of Equalization. 2025-26 California Consumer Price Index Letter to County Assessors Over a decade or two, this ceiling opens a widening gap between your assessed value and what your home would actually sell for. That gap is the tax benefit Prop 13 was designed to deliver.
What Your Tax Bill Actually Looks Like
Prop 13 caps the base property tax rate at 1% of your assessed value. If your Factored Base Year Value is $500,000, the base levy is $5,000.3Placer County. Proposition 13
What catches many homeowners off guard is that voter-approved bonds and special assessments stack on top of that 1%. School bonds, water district levies, and local infrastructure measures each add a fraction of a percent. The combined rate varies by tax rate area, but effective rates of 1.1% to 1.3% are common, and some areas run higher. These charges are set by local ballot measures, not by the assessor, and they appear as separate line items on your tax bill.3Placer County. Proposition 13
What Triggers a Full Reassessment
Two events reset your Base Year Value to current market value: a change in ownership, and new construction. Everything else leaves your existing assessment in place.
The most common trigger is a sale to an unrelated buyer. The assessor sets the new Base Year Value based on the purchase price, and the 2% annual cap starts fresh from that number. But not every transfer between people counts as a change in ownership. Transfers between spouses or registered domestic partners never trigger reassessment, including transfers resulting from divorce or death.4California Legislative Information. California Code Revenue and Taxation Code 63 Moving property into a revocable living trust, partnership, or LLC is also excluded, as long as the proportional ownership interests stay exactly the same. Putting your home into your own revocable trust is the standard example.
Legal entity transfers have their own rule. When a corporation, partnership, or LLC owns California real property, a transfer of more than 50% of the ownership interests in that entity, either in one transaction or cumulatively over time, triggers a full reassessment of the underlying real estate.5California Board of Equalization. Legal Entity Ownership Program – Definition of Change in Ownership
Parent-Child and Grandparent-Grandchild Transfers Under Proposition 19
This is where the rules changed sharply. Proposition 19, effective February 16, 2021, repealed the old parent-child exclusions that had been in place since 1986. The prior rules allowed parents to pass a primary residence of any value, plus up to $1 million in other property, to their children without reassessment. Those rules are gone.6California Board of Equalization. Exclusions from Reappraisal Frequently Asked Questions
Under Proposition 19, the exclusion for transfers between parents and children (or grandparents and grandchildren where the parents are deceased) survives only if two conditions are met. The property must be the transferor’s principal residence, and the child receiving it must make it their own principal residence within one year and apply for the homeowner’s or disabled veterans’ exemption.7California State Board of Equalization. Proposition 19 Investment properties, vacation homes, and commercial real estate no longer qualify.
Even for a qualifying family home, the exclusion has a value cap. The assessed value is fully preserved only if the property’s current market value does not exceed the existing Factored Base Year Value plus an inflation-adjusted threshold (currently $1,044,586 for transfers occurring between February 16, 2025, and February 15, 2027). If the market value exceeds that sum, the excess gets added to the assessed value.7California State Board of Equalization. Proposition 19 If a home has a Factored Base Year Value of $300,000 and a market value of $1,500,000, the new assessed value works out to roughly $500,000 rather than $300,000, because the $200,000 above the cap gets added on.
Family farms qualify under a similar provision. Grandparent-to-grandchild transfers are eligible only if the grandchild’s parents are deceased at the time of transfer. The claim form must be filed within three years of the transfer or before the property is sold to a third party, whichever comes first.7California State Board of Equalization. Proposition 19 Missing that deadline is one of the most expensive mistakes in California estate planning.
Carrying Your Low Assessment to a New Home
Proposition 19 also expanded the ability of certain homeowners to carry their low assessed value to a replacement home anywhere in California. Before Prop 19, this portability was limited to the same county or a handful of participating counties. It now works statewide.
You qualify if you are at least 55 years old, severely disabled, or a victim of a wildfire or natural disaster. You must buy or build a new primary residence within two years of selling the original one.8California State Board of Equalization. Proposition 19 Base Year Value Transfer Guidance Questions and Answers Homeowners who are 55 or older or severely disabled can use this transfer up to three times. Disaster victims have no limit.
If your replacement home costs the same as or less than the original, you carry over your old assessed value. If it costs more, the difference between the two sale prices gets added to your transferred Base Year Value.8California State Board of Equalization. Proposition 19 Base Year Value Transfer Guidance Questions and Answers Either way, you avoid resetting to full market value. The claim form must be filed within three years of buying the replacement home, though a late filing still qualifies for prospective relief from the year the claim is submitted.
How New Construction Changes Your Assessment
New construction is the second reassessment trigger, but it works differently from a sale. Only the value of the new work gets reassessed at current market value. The original structure keeps its existing Factored Base Year Value, producing a blended assessment on the property.
New construction means any addition or alteration that substantially adds value or extends the property’s useful life. Adding a bedroom, building a detached garage, or installing a pool all count. Routine maintenance and cosmetic repairs do not.9California State Board of Equalization. Assessors Handbook Section 410 – Assessment of Newly Constructed Property The assessor determines the market value of the newly built portion on its date of completion and adds that figure to the existing factored value. From then on, both pieces are subject to the 2% annual cap.
One important nuance: the assessor adds the market value the improvement contributes, not what you spent. If you paid $150,000 for a remodel but it added $120,000 in market value, the assessment increase is based on $120,000.9California State Board of Equalization. Assessors Handbook Section 410 – Assessment of Newly Constructed Property
For multi-year projects, the assessor can assess any portion that is complete and usable as of the January 1 lien date each year, phase by phase, with the full new construction value finalized once everything is done.
Solar Panels Do Not Increase Your Assessment
Installing solar is one of the few major improvements that will not raise your property tax bill. California law excludes qualifying active solar energy systems from being assessed as new construction, so the installation adds no value to your assessed total.10California Board of Equalization. Active Solar Energy System Exclusion
Qualifying systems include those used for water heating, space heating and cooling, and electricity production. Solar pool heaters, hot tub heaters, passive solar designs, and wind energy systems do not qualify. The exclusion is authorized through the 2025–26 fiscal year, with the statute scheduled to sunset on January 1, 2027.10California Board of Equalization. Active Solar Energy System Exclusion
Supplemental Tax Bills After a Reassessment
When you buy a property or finish new construction, your annual tax bill does not adjust on its own mid-year. Instead, the assessor issues a separate supplemental assessment covering the difference between the old assessed value and the new one, prorated for the months remaining in the fiscal year (July 1 through June 30).11California State Board of Equalization. Supplemental Assessment
Proration starts on the first day of the month after the reassessment event. Close on a home purchase in October and your supplemental bill covers November through June, eight months of the fiscal year. If the event occurs between January and May, you will receive two supplemental bills: one for the rest of the current fiscal year and a second covering the full next fiscal year that starts the following July 1.11California State Board of Equalization. Supplemental Assessment New homeowners who are not expecting that second bill sometimes mistake it for an error. It isn’t.
If the reassessment actually lowered your value (you bought a home for less than its prior assessed value, for instance), the supplemental assessment runs in reverse and you get a refund.
When the Market Drops: Proposition 8 Reductions
The 2% cap works in your favor when the market is rising, but a separate provision protects you when prices fall. Proposition 8, passed in November 1978, requires the assessor to temporarily reduce your assessed value whenever your property’s current market value drops below its Factored Base Year Value.12California Board of Equalization. Decline in Value – Proposition 8 You always pay taxes on whichever number is lower.
The assessor is supposed to monitor market conditions annually as of the January 1 lien date. If values recover, your assessed value can jump by more than 2% in a single year, but it can never climb above the Factored Base Year Value you would have had without the downturn. Once your assessment is back on that original track, the normal 2% cap resumes.12California Board of Equalization. Decline in Value – Proposition 8 The reduction is supposed to happen automatically, but requesting a review from the assessor’s office is often what gets it moving.
Appealing the Assessor’s Value
If you believe the assessor set your Base Year Value too high, or overvalued the property after a reassessment, you can file a formal appeal with your county’s Assessment Appeals Board. There is no fee in most California counties.
The regular filing window opens July 2 each year. It closes September 15 in counties where the assessor mails assessment notices to all property owners on the secured roll by August 1. In all other counties, the deadline runs through November 30.13California State Board of Equalization. County Assessment Appeals Filing Period for 2025 If you are appealing a supplemental assessment from a recent purchase or construction, the deadline is 60 days from the date the supplemental notice was mailed.14California State Board of Equalization. Assessment Appeals Frequently Asked Questions
You bear the burden of proving the assessor’s value is too high. The strongest evidence is comparable sales data: recent sales of similar properties near your valuation date. Look for properties sold within the past six to twelve months that are close in size, age, condition, and location. Three to five solid comparables usually make a more persuasive case than a single sale. The appeals board weighs evidence from both sides, so come with documentation rather than just a sense that your bill is too high. For a high-value property, hiring a certified appraiser to prepare an independent valuation can meaningfully strengthen your case.