California property tax assessment starts with what you paid for your home, not what it’s worth today. Under Proposition 13, the county assessor records a “base year value” when you buy or build, then increases it by no more than 2% each year. Your annual tax bill is 1% of that assessed value, plus voter-approved local charges. The assessed value only jumps to current market value when something specific triggers a reset, most often a sale or new construction.
That gap between what your home would sell for and what it’s taxed at can grow substantial over years of ownership. Understanding what preserves the low base, and what destroys it, is where the real money lives.
How Proposition 13 Sets Your Assessed Value
Article XIII A of the California Constitution caps the general property tax levy at 1% of a property’s “full cash value.”1Justia. California Constitution Article XIII A – Tax Limitation Your actual bill usually runs slightly above 1% because voter-approved bonds and special district charges get added on top, but the base levy itself is fixed.
The “full cash value” starts with either the 1975–76 tax roll value or, for property purchased or built after that, the appraised value at the time of purchase or completion. Each year the assessor multiplies that base year value by an inflation factor capped at 2%.2Justia. California Constitution Article XIII A – Tax Limitation – Section 2 For the 2025–26 assessment year, the Board of Equalization set the factor at exactly 2%. The result is your “factored base year value,” and it stays on the books, growing slowly, until a triggering event resets it.
The lien date is January 1. Whatever the property is worth on that date determines the assessment for the fiscal year running July 1 through June 30.
What Triggers a Full Reassessment
Two events reset your base year value to current market value: a change in ownership and new construction.
A change in ownership is any transfer of a real property interest where what’s transferred roughly equals full ownership.3California Legislative Information. California Revenue and Taxation Code – Implementation of Article XIII A A standard sale between unrelated parties is the textbook example. Gifts, inheritance outside certain family exclusions, and transfers of controlling interests in entities that own property can also qualify. When a change in ownership occurs, the assessor appraises the property at its full cash value on the date of the transfer, and that value becomes the new base year value.4California Legislative Information. California Revenue and Taxation Code 75.10
New construction triggers assessment too, but only on the added value. Adding a room, building a pool, or converting a garage into living space gets its own separate base year value based on market value at completion. The existing structure keeps its original protected base.4California Legislative Information. California Revenue and Taxation Code 75.10 A $500,000 home with a $100,000 kitchen remodel doesn’t become a $600,000 assessment. The house keeps its factored base, and the kitchen gets its own $100,000 base that begins its own 2% annual growth track.
When a property changes hands, the new owner must file a Preliminary Change of Ownership Report with the county recorder at recording. A separate Change in Ownership Statement goes to the assessor within 45 days if the change isn’t recorded, or within 150 days for transfers caused by a death. Failing to file after a written request from the assessor triggers a penalty of $100 or 10% of the taxes on the new base year value, whichever is greater.5Justia. California Revenue and Taxation Code 480-487 – Change in Ownership Reporting
Transfers That Don’t Trigger Reassessment
Not every ownership change resets your tax base, and knowing the exclusions is where owners save real money.
Transfers between spouses are completely excluded. That covers adding a spouse to the deed, transferring property because of divorce or legal separation, transfers into a trust for a spouse’s benefit, and transfers that take effect when a spouse dies.6California Legislative Information. California Revenue and Taxation Code 63
Beyond spousal transfers, the law excludes several other transactions:7California Legislative Information. California Revenue and Taxation Code 62
- Transfers into your own revocable trust, where you remain the beneficiary or retain power to revoke.
- Changes in how co-owners hold title, such as switching from joint tenancy to tenants in common without changing anyone’s proportional interest.
- Refinancing, since creating, assigning, or reconveying a security interest is not a transfer for reassessment purposes.
- Adding yourself to a joint tenancy where you’re one of the joint tenants after the transfer.
The thread running through the exclusions: if no one’s actual economic interest in the property changed, the assessor can’t reset the base. Get this wrong and you may not find out until a supplemental tax bill arrives months later. When in doubt, ask the county assessor’s office before recording any deed.
Supplemental Tax Bills After a Reset
When a reassessment happens mid-year, the county doesn’t wait for the next regular bill. The assessor calculates the difference between the old assessed value and the new one, then prorates that difference across the months remaining in the fiscal year.8California State Board of Equalization. Supplemental Assessment
A purchase that closes in October uses a proration factor of 0.75, since nine months remain. A January closing uses 0.50. The earlier in the fiscal year the event occurs, the larger the supplemental bill.
Timing also affects how many bills you receive. Events between June and December produce one supplemental bill covering the remainder of the current fiscal year. Events between January and May generate two: one for the rest of the current fiscal year and a second covering the full next fiscal year starting July 1.8California State Board of Equalization. Supplemental Assessment Buyers who close escrow in March or April are sometimes startled to receive two extra bills on top of their regular annual assessment.
If a reassessment produces a lower value, which happens occasionally with distressed property, the supplemental assessment produces a refund rather than a bill.
Proposition 19: Base Transfers and Family Rules
Proposition 19, phased in starting in 2021, changed two important pieces of the reassessment framework. It expanded who can carry a low tax base to a new home, and it sharply restricted the old parent-child exclusion.
Transferring Your Tax Base to a New Home
Homeowners who are at least 55 years old, severely disabled, or victims of a wildfire or natural disaster can transfer their existing base year value to a replacement primary residence anywhere in California.9California State Board of Equalization. Proposition 19 Before Proposition 19, this transfer was limited to the same county or a handful of participating counties and could only be used once. It now works statewide and can be used up to three times.
The replacement home must be purchased or newly constructed within two years of selling the original. If the replacement costs more than the original’s market value, the excess gets added to the transferred base. The “equal or lesser value” threshold shifts based on timing: 100% of the original’s sale price if you buy the replacement first, 105% if you buy within the first year after selling, and 110% in the second year.9California State Board of Equalization. Proposition 19
Parent-Child and Grandparent-Grandchild Transfers
For family transfers on or after February 16, 2021, the rules tightened. A parent can pass a primary residence to a child without full reassessment only if the child moves in and uses it as their own primary residence within one year and files for the homeowners’ or disabled veterans’ exemption in that same window.10California State Board of Equalization. Proposition 19 Fact Sheet – Intergenerational Transfer Exclusion
Even with those conditions met, there’s a value limit. If the property’s current market value exceeds the parent’s factored base year value by more than a set adjustment amount, the excess gets added to the transferred base. For transfers between February 16, 2025 and February 15, 2027, the adjustment is $1,044,586.10California State Board of Equalization. Proposition 19 Fact Sheet – Intergenerational Transfer Exclusion If a parent’s base year value is $200,000 and the home is worth $1,500,000, the child’s new base becomes $200,000 plus the amount exceeding $1,244,586, adding $255,414 to the base.
Family farms work under the same framework, but the child doesn’t have to live on the property. The land must be actively used for agriculture. Grandparent-to-grandchild transfers qualify only when the grandchild’s parent, who would have been the grandparent’s child, is deceased.10California State Board of Equalization. Proposition 19 Fact Sheet – Intergenerational Transfer Exclusion
The claim must be filed on the appropriate Board of Equalization form (BOE-19-P for parent-child, BOE-19-G for grandparent-grandchild) within three years of the transfer. Late claims can still be granted, but the exclusion applies starting the year the claim is filed rather than retroactively.
When Values Fall: Proposition 8 Reductions
Proposition 13’s 2% cap helps during booms. Proposition 8 protects you during downturns. If your property’s current market value on the January 1 lien date falls below its factored base year value, the assessor must temporarily reduce the assessment to that lower market value.11California State Board of Equalization. Decline in Value – Proposition 8 Many county assessors review properties proactively during broad market declines, but filing a request makes sure yours gets looked at.
These reductions are temporary. The assessor reviews them every year, and as the market recovers, the assessed value climbs back up toward the factored base year value. It won’t jump past that base. Once market value meets or exceeds the factored base, the regular Proposition 13 cap takes over again.
Disaster Relief for Damaged Property
Property damaged or destroyed by a disaster qualifies for reassessment relief under Revenue and Taxation Code Section 170. The damage must reduce market value by at least $10,000, and every California county has adopted the ordinance needed to provide the relief.12California Legislative Information. California Revenue and Taxation Code 170 The assessor recalculates value based on the property’s damaged condition, reducing the bill accordingly.
You must file with the county assessor within the timeframe set by your county’s ordinance or within 12 months of the disaster, whichever gives you more time.12California Legislative Information. California Revenue and Taxation Code 170
Owners whose homes were substantially damaged or destroyed in a Governor-proclaimed disaster can also transfer their base year value to a comparable replacement property in the same county, or to a replacement in another county if that county accepts such transfers. Proposition 19 added the option for disaster victims to transfer the taxable value of a primary residence to a replacement purchased or newly constructed within two years, filed on the appropriate form within three years for full retroactive relief.13California State Board of Equalization. Disaster Relief
The Homeowners’ Exemption
If you live in the home you own as your primary residence, you can claim the homeowners’ exemption, which reduces your assessed value by $7,000 before the tax rate is applied.14California State Board of Equalization. Property Tax Savings – Homeowners’ Exemption At the 1% base rate, that’s about $70 in annual savings. Modest, but free. The exemption doesn’t apply to rental property, vacation homes, or property where the owner receives a veterans’ exemption. You apply through the county assessor, and once granted, it stays in place until you move out or sell.
How to Challenge Your Assessment
If you believe your property is assessed above its actual market value, you can file a formal appeal. Start by gathering evidence: the assessed value from your tax bill, your opinion of true market value, and data to back that up. Comparable sales of similar nearby properties that closed near the January 1 lien date are the strongest evidence. Records of physical defects, deferred maintenance, or environmental issues that depress value also help.
Before filing formally, contact the assessor’s office directly. Staff will sometimes review your evidence informally and correct a value without a hearing.15California State Board of Equalization. Assessment Appeals Frequently Asked Questions That resolves most meritorious disputes faster and with less friction.
Filing Deadlines
The standard filing window runs July 2 through September 15. In counties where the assessor doesn’t mail value notices to all property owners by August 1, the deadline extends to November 30.16California Legislative Information. California Revenue and Taxation Code 1603 Many larger counties, including Los Angeles, use the November 30 deadline.17County of Los Angeles Assessment Appeals Board. Assessment Appeals Board Missing the deadline forfeits your appeal for that fiscal year. Verify the date with your county’s Clerk of the Board of Supervisors well in advance.
Filing Fees
Most counties charge a non-refundable filing fee, and the amounts vary widely. Los Angeles County charges $46 per application.18Los Angeles County Board of Supervisors. Assessment Appeals Information Santa Clara County, starting in June 2026, charges $290 for residential properties and $675 for commercial or multifamily properties.19County of Santa Clara. Frequently Asked Questions Regarding the Assessment Appeals Process Check the fee before filing, because it may influence whether a small valuation dispute is worth pursuing.
What Happens at the Hearing
Once your application is accepted, you’ll receive a hearing notice by mail. The hearing is conducted by an independent Assessment Appeals Board or Hearing Officer that acts as a neutral decision-maker between you and the assessor’s office. Both sides typically exchange evidence beforehand.
The board has two years from the close of the filing period to hear and decide the case. If it doesn’t act in that window, and you haven’t agreed to an extension, your opinion of value on the application becomes the assessed value by default.20California Legislative Information. California Revenue and Taxation Code 1604 That default doesn’t kick in if you failed to provide complete information or if related litigation is pending.
If the board grants a reduction, the tax collector issues a refund or credits the difference against future payments. The decision applies only to the specific fiscal year appealed. If values remain too high in later years, you have to file again each year.
When Property Taxes Are Due
California secured property taxes are paid 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. Late payments trigger a 10% penalty on the delinquent installment, with a small additional cost on the second. These deadlines don’t move except when December 10 or April 10 falls on a weekend or holiday, in which case the deadline shifts to the next business day.
Supplemental tax bills follow their own schedule printed on the bill itself rather than the standard cycle. They arrive separately and at unpredictable times, which makes them easy to overlook. Penalties for missing supplemental deadlines are the same.