Assessed value in Los Angeles County is not market value because California law does not ask the Assessor to measure market value each year. It asks for the lesser of two numbers: the property's base year value, stepped up annually by a capped inflation factor, and its full cash value on the January 1 lien date (Revenue and Taxation Code section 51). The result is a taxable value for the tax roll, and it is not an appraisal. Market value is what the open market would most probably pay today, and that is the question an appraiser answers.
What is base year value?
Base year value is the value the law fixes for a property at a starting event, and it is the anchor of every California assessment. Section 110.1 names three possible starting points:
- The 1975 lien date, for property that has not been bought, newly built or changed in ownership since then.
- The date of a purchase or other change in ownership after that.
- The date new construction is completed, which gives the new work its own base year value.
On a purchase, section 110 presumes the purchase price is the full cash value when the deal was negotiated at arm's length between knowledgeable parties, unless the evidence shows the property would not have sold for that price in an open market transaction. The authority for all of this is Article XIII A, section 2 of the California Constitution.
How does the Assessor get from base year value to assessed value?
Every year after the base year, section 51 compounds the base year value by an inflation factor tied to the California Consumer Price Index, with an annual ceiling written into the statute. That produces the factored base year value. On each January 1, the lien date fixed by section 2192, the law compares the factored base year value with full cash value, the amount of cash or its equivalent the property would bring on the open market when neither buyer nor seller could take advantage of the other, and the lesser of the two goes on the roll.
Because the test is rerun every lien date, the answer can switch. In a falling market, full cash value may become the lesser number, and the Assessor enrolls it; this is the decline-in-value review the Los Angeles County Office of the Assessor describes on its own page. When the market recovers, the comparison runs again, and the taxable value can rise back toward the factored base year value, never past it.
Why is that not market value?
Three reasons, each built into the system.
- It is anchored to a past date. The factored base year value describes what the property was worth at its starting event, carried forward by a formula. A house bought long ago and a similar house bought last year can sit side by side with very different assessed values.
- It is made from records, at scale. The roll covers every parcel in the county. It is not built by measuring your gross living area, the finished space above grade, or by walking through to rate the kitchen and the roof, as an appraisal inspection is.
- Its intended use is tax. Intended use, what a valuation will be used for, decides its method. The roll exists to spread property tax under the Constitution's rules, not to tell a buyer, a lender or a court what a house would sell for.
Market value, by contrast, has a lending definition in federal rules (12 CFR 34.42): the most probable price a property should bring in a competitive and open market under all conditions requisite to a fair sale, buyer and seller each acting prudently and knowledgeably, the price not affected by undue stimulus. What is market value takes that definition apart in plain words.
What does this look like in Claremont, La Verne and Pomona?
Claremont, La Verne and Pomona all sit in Los Angeles County, so the same Assessor and the same Assessment Appeals Board apply. These are the kinds of situations that come in:
- A pre-1940 house near the Claremont Village and the Colleges held for a long time, where the base year sits far back and the factored value can trail the market.
- A postwar ranch house north of Foothill Boulevard with a permitted addition: the original house carries one base year value and the addition its own, from its completion date.
- A recently bought house in the same pocket, where the purchase price, under section 110's presumption, set a fresh base year value.
The Los Angeles County page describes the pockets and the Assessor's role in more detail. For the long-held case specifically, see why a long-held Claremont house shows a gap.
Where does an appraisal fit?
An appraisal is an independent opinion of market value as of a stated effective date, the date the opinion applies to, developed by a licensed appraiser under the Uniform Standards of Professional Appraisal Practice (USPAP). It is the document that measures market value when someone needs it measured: an estate as of a date of death, a family law matter, a lender, or an owner who believes full cash value on January 1 fell below the factored base year value.
For that last case, the appraisal is made as of the lien date and documents the closed sales and adjustments behind the opinion. The Assessor reviews, the board decides, and neither outcome is the appraiser's call. Confirm the current review and filing periods on the Assessor's and the board's own pages. Property tax appeals on the county line and the property tax appeal appraisal page describe that assignment.
What else is not market value?
An automated estimate from a portal is not an appraisal; it is a statistical estimate from records and nearby sales. An agent's comparative market analysis, or CMA, a licensed agent's opinion of a likely list or sale price, is not an appraisal. A cash offer is not an appraisal; it is one buyer's price on stated terms, and Mr. Cali Offers, a separate cash-offer brand that shares the Mr. Cali name, explains its offers at mrcalioffers.com/home-value.
The four different numbers guide sets all of them side by side, assessed value on both sides of the county line covers San Bernardino County, and the full cluster is in the value types knowledge center. If you are unsure which number your situation calls for, start with appraisal vs. estimate or call (909) 324-6122. Fees are set by the scope of the assignment, quoted before work begins, and do not depend on the value.
Sources
- California Revenue and Taxation Code section 51 (lesser of factored base year value or full cash value) (accessed October 30, 2026)
- California Revenue and Taxation Code section 110.1 (base year value) (accessed October 30, 2026)
- California Revenue and Taxation Code section 110 (full cash value; purchase price presumption) (accessed October 30, 2026)
- California Constitution, Article XIII A, section 2 (accessed October 30, 2026)
- California Revenue and Taxation Code section 2192 (lien date) (accessed October 30, 2026)
- Los Angeles County Office of the Assessor, decline in value (accessed October 30, 2026)
- Los Angeles County Assessment Appeals Board (accessed October 30, 2026)
- 12 CFR 34.42, definitions (market value) (accessed October 30, 2026)
Gordon Hall, California Certified Residential Real Estate Appraiser, BREA No. AR003877 (lookup: https://www2.brea.ca.gov/breasearch/faces/party/view.xhtml?id=23601). Reports are prepared in conformity with the Uniform Standards of Professional Appraisal Practice (USPAP). Nothing here is legal or tax advice; admissibility is always the court's decision.
Frequently asked questions
What is base year value in California?
Base year value is the value fixed for a property at its starting event under Revenue and Taxation Code section 110.1: the 1975 lien date, or the date of a later purchase or change in ownership, or the date new construction is completed. Each year it is stepped up by an inflation factor with an annual ceiling set in section 51.
Why doesn't the Los Angeles County Assessor just use market value?
Because the California Constitution and the Revenue and Taxation Code tell the Assessor to enroll the lesser of the factored base year value and full cash value on the January 1 lien date. Market value enters the roll at a purchase, a change in ownership or completed new construction, or when it falls below the factored base year value.
Is my Los Angeles County assessed value an appraisal of my house?
No. The assessed value is the taxable value on the county roll, set from records for tax purposes. It is not an appraisal, which is a licensed appraiser's independent opinion of market value as of a stated effective date, developed under USPAP.
What if I think my market value fell below my assessed value?
The Los Angeles County Office of the Assessor describes a decline-in-value review on its website, and formal appeals go to the Los Angeles County Assessment Appeals Board. Confirm the current periods on those pages. An appraisal as of the January 1 lien date can document market value; the county and the board decide what is enrolled. Nothing here is legal or tax advice.
