When is a property reassessed in California?
Two things reset an assessed value in California: a change of ownership, and the completion of new construction. A refinance, a transfer between spouses, and repairs or replacement that add nothing generally leave your base year value alone. Every one of those is a general rule with conditions under it rather than a guarantee, which is what the table below is for, and the Assessor's own change in ownership guidance is the current authority on a specific transfer. The LA County property tax estimator estimates a bill from a reset value.
New construction is the half people get wrong. Building an addition does not revalue the whole property: the county assesses what was built and adds it to the value you already had.
A change of ownership
A sale is the obvious one, and the new base year value is the price paid in an arm's length transaction. Less obvious transfers count too: adding or removing somebody from the title other than a spouse, a transfer into or out of certain trusts, and a change in the ownership of an entity that holds the property.
The practical consequence is the supplemental bill, which charges the difference between the old value and the new one for the rest of that fiscal year.
Completed new construction, and only the new part
A new unit, an addition, a conversion of space that was not living space: the county assesses the value the work added and adds it to your existing base year value. The rest of the house keeps the value it had, however old that is, which is the single most useful thing an owner can know before they build.
Ordinary maintenance and like-for-like replacement is not new construction. A new roof, a repaired foundation or replacement windows do not reassess anything. A new bathroom where there was none is on the other side of that line, and the boundary is a question for the Assessor on the specific work. Prop 13 explained covers why the untouched part keeps its old value.
If what you are weighing up is building a second unit, the ADU feasibility checker answers what the City of Los Angeles allows on a lot, and the tax side of it is this: the ADU is assessed at what it adds, and the house keeps its old value.
What does not reassess
A refinance alone is not a change of ownership, whatever the paperwork feels like. Nor, generally, is a transfer between spouses, or a transfer into a revocable living trust where the same person keeps the benefit. Correcting the way a name is spelled on a deed does not either.
The one to be careful with is adding a family member to the title for convenience or estate planning, which can be a partial change of ownership and can trigger a partial reassessment. That is worth asking the Assessor about before signing rather than after the notice arrives.
| Event | General rule | The condition |
|---|---|---|
| New construction | Reassessed, to the extent of the new construction. | The new work is assessed at its value when it is completed and the rest of the property keeps its base year value. Adding a bedroom does not revalue the house. |
| A refinance | Generally not a change in ownership. | A refinance on its own does not reassess the property. What matters is whether the beneficial ownership changed, which is a question about the transfer rather than about the loan. |
| A transfer between spouses | Generally excluded. | The interspousal exclusion is broad and it is not unconditional: statutory exceptions apply, so an unusual transfer is worth confirming with the Assessor before it is made. |
| A fall in market value | Relief is available and is not automatic. | Proposition 8 lets the Assessor enroll the lower of the factored base year value and current market value, but it takes an assessment review. Nobody applies it on your behalf because the market moved. |
| A home passing to a child or grandchild | An exclusion exists and is limited. | The Proposition 19 parent-child and grandparent-grandchild exclusions are subject to eligibility, claim deadlines and value limits, and the home generally has to become the heir's principal residence. Missing the deadline loses the exclusion rather than delaying it. |
LA County Property Tax Estimator
Estimates the annual property tax on an LA County property, including the homeowner's exemption and the supplemental bill a purchase triggers in the first year.
Inheritance, since 2021
Proposition 19 replaced the older parent-to-child and grandparent-to-grandchild exclusions from February 2021. A family home can still pass with its base year value in some circumstances, but the rules are tighter: the home generally has to become the heir's own principal residence, there is a claim to file, and the exclusion is capped at the transferred value plus an amount the state adjusts over time.
That cap is not quoted on this page on purpose. It is adjusted periodically, and a stale figure in an answer about an inheritance is the kind of wrong number somebody makes an irreversible decision on. The State Board of Equalization publishes the current amount and the Assessor's office handles the claim.
When a value can go down
If market value falls below your factored base year value, the taxable value is supposed to be the lower of the two. That is Proposition 8, and it is not automatic: you ask the Assessor for a decline-in-value review. A reduction granted this way is temporary and is reviewed each year as the market recovers, so it is a reduction in the taxable value rather than a change to your base year value.
Common questions
Does refinancing trigger a property tax reassessment?
Does adding my spouse to the title reassess the house?
If I inherit my parents' house, do I keep their low property tax?
Will building an ADU reassess my whole property?
Can my assessed value go down if the market falls?
Related guides
- Prop 13 explained: what it caps, and what it does notProposition 13 caps the tax rate at 1% and limits how fast an assessed value can rise. What it does not cap, and what resets it.
- The homeowner's exemption in Los Angeles CountyThe $7,000 homeowner's exemption takes about $87.50 a year off the tax on a home you live in. Who qualifies, how to claim it, and how to tell whether you have it.
- Your first-year supplemental property tax billAfter a purchase the county bills the difference between the old assessed value and yours, prorated from the month you bought. Buy between January and May and it comes twice.
The figures on this page were last checked by a person on October 16, 2026