How Does Property Tax Assessment Work in Los Angeles County?

In Los Angeles County, property tax assessment starts with the Assessor placing a taxable value on your parcel: what you paid when you bought it (or the cost of new construction), adjusted upward by no more than 2% each year under Proposition 13. That number, multiplied by the 1% base rate and added to voter-approved bonds and local direct assessments, becomes your annual bill. It resets to market value only when specific events happen, and you can push back on it through exemptions, a decline-in-value review, or a formal appeal.

How Proposition 13 Sets Your Assessed Value

California’s property tax system runs on one number: 1% of assessed value. Article XIIIA, Section 1 of the California Constitution caps the base ad valorem rate at that level.¹ Voter-approved bonds and special assessments get added on top, but the rate itself cannot go higher.

Your assessed value is fixed when you buy the property or complete new construction. After that, the Assessor can raise it by no more than 2% per year, tied to the California Consumer Price Index.² Revenue and Taxation Code Section 51 codifies the cap and holds it at 2% even if actual inflation runs higher.³ The adjusted figure is your factored base year value.

Everything is measured as of January 1, the lien date. That is when the tax claim attaches and when the Assessor values the property for the upcoming fiscal year. If your home’s market value doubled over fifteen years but you never sold, your assessed value climbed only 2% per year from what you paid. A neighbor who bought last year on the same block can owe far more on a comparable house.

What Actually Shows Up on Your Bill

The 1% base rate is only part of what you pay. Your bill also carries direct assessments submitted by local taxing agencies for specific projects or services. These are sometimes called non-ad valorem charges because they are not based on assessed value.⁴

The most common in Los Angeles County is a Mello-Roos special tax. Mello-Roos funds community facilities districts that were approved by a two-thirds vote, usually to pay for schools, roads, or infrastructure in newer developments. The bonds typically run 30 years and appear as a line item on your bill.⁵ Other direct assessments cover flood control, street lighting, or mosquito abatement. They can add hundreds or thousands to an annual bill, and none of them is capped by Proposition 13. Buyers in newer subdivisions get caught off guard by them often.

Events That Reset Your Assessed Value

A reassessment overrides the 2% cap and sets your taxable value at current market rate. Two events cause nearly all reassessments.

Change in Ownership

Revenue and Taxation Code Section 60 defines a change in ownership as any transfer of a present interest in real property where the value transferred is substantially equal to the full fee interest.⁶ A standard sale is the obvious example, but transfers into certain trusts, some corporate restructurings, and long-term leases can also count. Some family transfers are excluded under Proposition 19, covered below.

New Construction

Under Revenue and Taxation Code Section 70, adding to land or improvements, or making an alteration that amounts to major rehabilitation or changes the property’s use, triggers reassessment of the newly added value. A bedroom, garage, or pool qualifies. The Assessor values the new improvement at fair market value and adds it to your existing base year value, so only the new portion gets market-rate treatment.⁷

Routine maintenance does not count. Paint, carpet, and a new roof are upkeep and do not change assessed value. The line is whether the work creates something functionally new or simply keeps the existing structure working.⁷

Disaster and Calamity Relief

If your property is damaged or destroyed by a disaster without your fault, Revenue and Taxation Code Section 170 allows a temporary reassessment to reflect the reduced value. It covers Governor-declared disasters and localized events like a house fire. If the difference between value before and after the damage is $10,000 or more, the assessed value drops accordingly.⁸

You must file a written application within 12 months of the damage or by the deadline set by county ordinance, whichever is later. Once the property is repaired, the assessed value returns to what it would have been, adjusted for any Proposition 13 inflation factor that would have applied in the meantime.⁸

Proposition 19 and Family Transfers

Proposition 19 took effect February 16, 2021, and it narrowed the parent-child exclusion sharply while expanding base year transfers for older homeowners.

Parent-Child and Grandparent-Grandchild Transfers

Before Proposition 19, parents could pass a primary residence and up to $1 million in other real property to their children without reassessment. Now the exclusion applies only when the property was the parent’s primary residence and the child makes it their own primary residence within one year of the transfer.⁹ The child also has to file for the homeowners’ or disabled veterans’ exemption within one year. Investment properties and vacation homes no longer qualify at all.

Even for qualifying primary residences, there is a value cap. If current market value exceeds the parent’s assessed value by more than $1 million, the excess is added to the transferred base. A child inheriting a home with a $300,000 assessed value and a $2 million market value ends up with a new assessed value of $1,300,000: the $300,000 base plus the $700,000 above the $1 million cushion. Grandparent-to-grandchild transfers follow the same rules, but only when the grandchild’s parents who would have qualified as the grandparent’s children are deceased.⁹

Base Year Transfers for Homeowners 55 and Older

Proposition 19 also expanded the ability of homeowners age 55 or older, severely disabled homeowners, and wildfire or natural disaster victims to carry their current assessed value to a replacement home. Under Revenue and Taxation Code Section 69.6, the replacement can sit anywhere in California and can cost more than the original, though buying up adds the market-value difference to the transferred base.¹⁰

The replacement must be purchased or newly built within two years of selling the original, and qualified homeowners can use the benefit up to three times. Equal or lesser value carries the old assessed value forward without adjustment. The county defines equal or lesser as 100% of the original’s market value if you buy before selling, 105% if you buy in the first year after selling, and 110% if you buy in the second year.¹¹

The Supplemental Bill New Owners Miss

After a change in ownership or new construction, the Assessor recalculates value, and the difference between old and new generates a supplemental assessment. It arrives as a separate bill, not a change to your regular annual bill.¹²

The supplemental tax is prorated. The county treats the event as happening on the first of the month after the actual date, then taxes you on the new value for the remainder of the fiscal year. Close on a home in October and you owe supplemental taxes for roughly 75% of the current fiscal year. Section 75.41 sets the proration factors by month.¹³ New buyers whose purchase spans the gap between fiscal years often get two supplemental bills.

Supplemental bills go directly to the owner, even when you have an impound account. Lenders rarely pay them automatically, so ignoring the envelope is one of the most common tax mistakes new homeowners make.¹²

Exemptions That Lower Your Assessed Value

Several exemptions reduce assessed value, but the Assessor does not grant them automatically. You have to apply.

Homeowners’ Exemption

Own and occupy a home as your principal residence on January 1 and you qualify for a $7,000 reduction in assessed value.¹⁴ At the 1% base rate, that saves roughly $70 a year before voter-approved additions. Modest, but many homeowners never file the one-time application. It doesn’t cover rental properties, vacation homes, or homes vacant or under construction on the lien date.

Disabled Veterans’ Exemption

Veterans with a 100% service-connected disability rating, or who are compensated at the 100% rate for individual unemployability, get a much larger reduction. For the 2026 assessment year, the basic exemption reduces assessed value by $180,671 with no income limit. A low-income tier raises the reduction to $271,009 if total household income from the prior year is $81,131 or less.¹⁵ The property has to be the veteran’s principal residence. The basic exemption is a one-time filing; the low-income exemption usually needs annual renewal by February 15.

Welfare Exemption for Nonprofits

Property owned and operated by qualifying charitable, religious, hospital, or scientific organizations can be fully exempt. The organization needs a current federal or state tax-exempt letter, and its formation documents must irrevocably dedicate the property to a qualifying purpose. The Board of Equalization decides whether the organization qualifies; the county Assessor decides whether the specific property qualifies based on actual use.¹⁶ Holding 501(c)(3) status alone is not enough, since some 501(c)(3) purposes fall outside the welfare exemption’s categories.

When the Market Drops: Proposition 8

Proposition 13 caps how fast your value can rise. Revenue and Taxation Code Section 51 also protects you when values fall. Each year, the Assessor is supposed to set your taxable value at the lesser of your factored base year value or current market value.³ If the local market drops below your Proposition 13 base, you are entitled to the lower number.

This is commonly called a Proposition 8 reduction. The Assessor may automatically lower values during a downturn, but the office does not catch every property. If you believe market value has dipped below assessed value and nothing has changed, you can request a decline-in-value review or file a formal appeal. Once the market recovers and full cash value climbs back above the factored base, the Assessor returns you to the Proposition 13 base and resumes the 2% annual cap.³

Challenging Your Assessment

The Informal Review

Before filing a formal appeal, you can ask the Assessor’s office for an informal decline-in-value review. The window runs July 2 through November 30, the same as the formal appeal period.¹⁷ The Assessor reviews comparable sales and may agree to reduce your value without a hearing.

The catch trips people up every year: requesting an informal review does not protect your right to a formal appeal. Wait for the informal response, let November 30 pass, and you have lost the ability to take it further. File the formal appeal as a backup any time there is a chance you might need it.¹⁷

The Formal Appeal

Formal appeals go to the Assessment Appeals Board, not the Assessor. The filing window for the regular assessment roll runs July 2 through November 30. If November 30 falls on a weekend or legal holiday, a postmark by the next business day is timely.¹⁸ There is no extension for forgetting.

Start by locating your Assessor’s Parcel Number on your annual bill or through the Assessor’s online property search. Then gather comparable sales of similar homes near yours that closed around the January 1 lien date. The best comparables match yours in size, age, condition, and location. An independent appraisal can support your case, and detailed photos of structural problems, deferred maintenance, or other value-reducing conditions help when your argument rests on the physical state of the property.

The application is Form AAB-100.¹⁹ It asks for your opinion of value, the specific dollar amount you believe the property is worth. Choose that number carefully. It matters later. Most homeowners select “decline in value” as the reason, citing market conditions or property-specific deficiencies. The filing fee is $46 per parcel, non-refundable.¹⁸ Applications can be filed online or mailed to the Board’s office in the Kenneth Hahn Hall of Administration.¹⁷

The Hearing

The Assessment Appeals Board is a quasi-judicial body separate from the Assessor. It was established by the Board of Supervisors under Article XIII of the California Constitution to settle valuation disputes.²⁰ You and a representative from the Assessor’s office both present evidence under oath. The Board weighs the comparable sales, appraisals, and other documentation and either adjusts the value or upholds it. Decisions are often announced at the hearing, with a written notice by mail. The result applies only to the tax year under appeal; a recurring problem needs a new application for each year.

The Two-Year Rule

Revenue and Taxation Code Section 1604 gives the Board two years from timely filing to make a final determination. If it fails to act within that window, your opinion of value on Form AAB-100 becomes the enrolled assessment for the tax years the application covers.²¹ Two exceptions: the deadline does not apply if you and the Board mutually agree to extend the timeline, or if your application is consolidated with another of yours that already has an agreed extension. The rule also will not protect you if you failed to provide complete information as required by law.

Each party gets one postponement as a matter of right. Requesting that postponement within 120 days of the two-year deadline requires you to sign a written agreement tolling the clock indefinitely, terminable only with 120 days’ written notice.²² Signing that extension without understanding it is where many homeowners give up their strongest piece of leverage.

1
Justia. California Constitution Article XIII A Section 1 – Tax Limitation
2
California Legislative Information. California Constitution Article XIII A – Tax Limitation
3
California Legislative Information. California Code Revenue and Taxation Code 51 – Valuation of Real Property
4
Los Angeles County Auditor-Controller. Direct Assessments
5
Los Angeles County Auditor-Controller. What Is a Mello Roos Assessment
6
California Legislative Information. California Code Revenue and Taxation Code 60 – Change in Ownership and Purchase
7
California State Board of Equalization. New Construction
8
California Legislative Information. California Code Revenue and Taxation Code 170
9
California Legislative Information. California Revenue and Taxation Code 63.2
10
California Legislative Information. California Code Revenue and Taxation Code 69.6
11
California State Board of Equalization. Proposition 19
12
Treasurer and Tax Collector – Los Angeles County. New Property Owner
13
California Legislative Information. California Code Revenue and Taxation Code 75.41
14
Los Angeles County Assessor. Homeowners Exemption
15
California State Board of Equalization. Letter to Assessors 2025-014 – Disabled Veterans Exemption Increases for 2026
16
California State Board of Equalization. Property Tax Welfare Exemption
17
Los Angeles County Assessor. Contesting Your Assessed Value
18
Los Angeles County Board of Supervisors. Assessment Appeals Information
19
Los Angeles County Board of Supervisors. AAB Resources
20
Los Angeles County Board of Supervisors. Assessment Appeals
21
California Legislative Information. California Code Revenue and Taxation Code 1604
22
Cornell Law Institute. California Code of Regulations Title 18 Section 323 – Postponements and Continuances