California commercial property tax starts at a base rate of 1% of assessed value under Proposition 13, and most commercial owners end up paying between 1.1% and 1.25% once voter-approved bond debt is added. The number that really drives your bill is the assessed value, which is locked at the purchase price and can rise no more than 2% per year until a change in ownership or new construction triggers a full reassessment to current market value. That system produces wide gaps between what neighboring buildings pay, and it is the reason a routine transaction or partial-interest transfer can send a tax bill up by six figures overnight.
How Your Assessed Value Is Set and Grows
Proposition 13, adopted by California voters in 1978, gives every property a “base year value” equal to its fair market value at the time of purchase or completion of new construction. Properties that have not changed hands since before 1975 use the 1975-76 assessed value as their base.1California State Assembly. Proposition 13 and Local Tax Authority
Each January 1, the county assessor increases that base by the lesser of 2% or the change in the California Consumer Price Index. For the 2025-26 assessment year, the Board of Equalization set the inflation factor at the full 2%.2California State Board of Equalization. 2025-26 California Consumer Price Index The result is called the “factored base year value,” and it drives your tax bill every year absent a reassessment event or a decline in market value.3California Legislative Information. California Revenue and Taxation Code 51
When the Market Falls Below Your Assessed Value
Proposition 8, passed later in 1978, requires the assessor to enroll the lower of two numbers each January 1: the factored base year value or the property’s current market value.4California State Board of Equalization. Decline in Value – Proposition 8 If your building’s market value has dropped below its assessed value, you are entitled to a temporary reduction. Some assessors review properties on their own; if yours does not, you can file an assessment appeal.
A Prop 8 reduction is temporary. Once the market recovers, the assessor can raise your assessed value by more than 2% per year until it reaches your factored base year value again. It will not exceed that ceiling without a change in ownership or new construction, but the climb back can be steep.4California State Board of Equalization. Decline in Value – Proposition 8 Budget accordingly; a big reduction in a down year can reverse quickly.
What Triggers a Full Reassessment
Outside the annual inflation adjustment, assessed value resets to current fair market value only when a “change in ownership” or “new construction” occurs. Either event creates a new base year value, and the 2% growth cycle starts over from that number.
Change in Control of a Legal Entity
A straight sale of a commercial building obviously triggers reassessment, but the entity rules catch more owners off guard. Reassessment occurs when any person or entity gains direct or indirect control of more than 50% of the ownership interests in a corporation, partnership, LLC, or other legal entity that holds the property, including through multi-tiered parent structures.5Legal Information Institute. California Code of Regulations Title 18 462.180 – Change in Ownership-Legal Entities
A separate rule applies to property that was originally contributed to an entity tax-free. If the original owners cumulatively transfer more than 50% of their interests, whether in one transaction or many over time, the underlying real estate gets reassessed on the date the 50% threshold is crossed.5Legal Information Institute. California Code of Regulations Title 18 462.180 – Change in Ownership-Legal Entities Small partial-interest sales that seem harmless individually can add up to a reassessment years later.
After any change in control, the acquiring entity must file a Change in Ownership Statement (Form BOE-100-B) with the Board of Equalization within 90 days. Missing the deadline results in a penalty of 10% of the taxes on the property’s new base year value.6California Legislative Information. California Revenue and Taxation Code 480-1 On a high-value commercial property, that alone can run into tens of thousands of dollars, and as noted below, non-filing keeps the escape-assessment window open indefinitely.
Inherited Commercial Property Under Proposition 19
Before February 2021, parents could pass commercial property to their children without reassessment, up to $1 million in factored base year value. Proposition 19 eliminated that exclusion for everything other than a principal residence or family farm.7California State Board of Equalization. Proposition 19 Inherit a commercial building today and it gets reassessed to current market value. For families holding buildings under decades-old Prop 13 bases, the increase can be severe.
New Construction (With a Solar Carve-Out)
Additions or alterations that substantially increase a property’s value or change its use count as new construction and trigger reassessment of the new work. Adding a floor to an office building or converting a warehouse to retail qualifies. Routine maintenance and cosmetic repairs do not.
One exception matters for commercial owners: installing an active solar energy system is excluded from the definition of new construction through the 2025-26 fiscal year, and the exclusion is currently set to expire on January 1, 2027. It covers systems that produce electricity, heat water, or provide space conditioning, but not pool heaters or passive solar designs.8California State Board of Equalization. Active Solar Energy System Exclusion
Supplemental and Escape Assessments
When a change in ownership or new construction occurs, you will not wait until the next regular tax bill to feel it. California issues supplemental assessments to capture the difference between the old and new assessed value, prorated for the remaining months in the fiscal year (July 1 through June 30).9California State Board of Equalization. Supplemental Assessment
Timing determines how many supplemental bills arrive. Events between June and December generate one supplemental bill for the rest of that fiscal year. Events between January and May generate two: one for the remaining months of the current year and another for the entire following year.9California State Board of Equalization. Supplemental Assessment These are separate from the regular annual bill, and a supplemental reduction will not offset what you owe on the regular bill. Pay the original in full.
Escape assessments correct undertaxation from prior years retroactively. The general lookback is four years. If you failed to file a required Change in Ownership Statement or concealed taxable personal property, the window extends to eight years. Where fraud is involved, or where the BOE-100-B for an entity control change was never filed, there is no time limit at all.10California State Board of Equalization. Statute of Limitations for Supplemental and Escape Assessments Filing your ownership-change paperwork on time is not just about avoiding a penalty; it closes the door on indefinite retroactive assessment.
What Actually Shows Up on the Tax Bill
Total property tax has several layers. The foundation is the 1% general levy from Proposition 13, applied uniformly to all property types statewide.1California State Assembly. Proposition 13 and Local Tax Authority
Layered on top are voter-approved debt service rates for general obligation bonds, typically funding schools, community colleges, and public infrastructure. These add roughly 0.1% to 0.25% in most locations, putting total ad valorem rates in the 1.1% to 1.25% range for the majority of California commercial properties.
Mello-Roos special taxes are a separate line item and can add significantly to a bill, especially in newer developments. Created under the Mello-Roos Community Facilities Act of 1982, these are levied within designated Community Facilities Districts to fund infrastructure like roads, water systems, and schools. They are not tied to assessed value; they are fixed amounts or formula-based charges approved by a two-thirds vote of property owners or registered voters within the district.
Direct assessments round out the bill as separate charges for services like flood control, sewer, lighting maintenance, and weed abatement. If you are evaluating a purchase, pull a full recent tax bill rather than estimating from the 1% rate. Mello-Roos and direct assessments can add thousands of dollars that a simple assessed-value calculation will miss.
Business Personal Property
Commercial property tax reaches beyond real estate. Machinery, equipment, furniture, computers, leasehold improvements, and other tangible personal property used in your business are taxable, and each year the county assessor may require you to file a Business Property Statement (Form 571-L) listing these assets and their costs.
The filing window opens on January 1 (the lien date) and closes at 5:00 p.m. on April 1, though filings are accepted without penalty through May 7.11Taxes (State of California). Property Tax Function Important Dates Missing May 7 adds a penalty of 10% of the assessed value of the unreported taxable personal property. The penalty can be waived on a showing of reasonable cause beyond your control, if you apply to the county board in time.
County assessors are required to conduct a significant number of business property audits each year, benchmarked against historical audit volumes for assessees with $400,000 or more in business personal property.12California State Board of Equalization. Business Property Audits If you own substantial equipment or fixtures, expect a review at some point. Keeping accurate fixed-asset schedules from the start is far cheaper than reconstructing them under audit.
Payment Deadlines and Delinquency
The annual secured tax bill splits into two installments. The first is due November 1 and delinquent after December 10. The second is due February 1 and delinquent after April 10. When a delinquency date falls on a weekend or holiday, it moves to the next business day.11Taxes (State of California). Property Tax Function Important Dates
A 10% penalty is added to each delinquent installment. If taxes remain unpaid as of June 30, the property becomes tax-defaulted, and interest starts accruing at 1.5% per month on the unpaid balance. That is 18% annualized and compounds fast on a commercial bill. After five years in default, the county tax collector can sell the property at a tax sale.
Unsecured taxes (on business personal property not tied to real estate) follow a different schedule, with payment due by August 31.11Taxes (State of California). Property Tax Function Important Dates
Appealing an Assessment
If your assessed value exceeds fair market value as of the January 1 lien date, file an Application for Changed Assessment with your county’s Assessment Appeals Board. The filing window opens July 2 every year. Closing dates split by county: where the assessor mails value notices to all secured-roll owners by August 1, the deadline is September 15; in all other counties, it is November 30.11Taxes (State of California). Property Tax Function Important Dates Los Angeles, San Diego, Orange, Riverside, and San Francisco each fall into one category or the other, so confirm your county’s date before assuming late November.
For supplemental or escape assessments, the appeal window shrinks to 60 days from the mailing date of the notice or tax bill. That deadline is easy to miss on a recent purchase where mail forwarding is not yet reliable.
Your appeal needs evidence that the assessor’s value is too high. The three standard approaches are comparable sales, the cost approach (replacement cost minus depreciation), and income capitalization (net income divided by a market-derived cap rate). Income capitalization tends to carry the most weight for commercial property because buyers price buildings on the income they generate. Rent rolls, operating expense data, and recent comparable sales strengthen a filing considerably.
Pay the bill in full while the appeal is pending. Skipping payment to wait for a decision triggers the same delinquency penalties described above. If the board grants a reduction, the county issues a refund for the overpayment.