Home and Money · Reviewed July 14, 2026
Prop 13 and California property tax basics
The property-tax bill has a logic. Start with the base-year value and the 1 percent levy, then see what can move the number.
The short version
The taxable value follows one track; the bill has others
Prop 13 usually limits how fast the property's factored base-year value rises, not the whole tax bill. So the total due can still change: a sale, completed construction, voter-approved debt, assessments, and direct charges can all move it.
What changes the answer: A temporary Proposition 8 value can rise by more than 2 percent while it returns toward the Prop 13 factored base-year value.
Think of Prop 13 as the track for the taxable value, not a promise that the whole bill stays still. A property's base-year value is usually set at market value when it changes ownership. Completed new construction can add a new value for the new work.
The county assessor then factors that base-year value forward each year. The annual inflation adjustment cannot be more than 2 percent, but it can be lower. A temporary decline-in-value assessment follows a different path until market value catches back up with the factored base-year value.
The basic countywide property-tax levy is 1 percent of taxable value. Voter-approved bond debt can add an ad valorem rate. Special taxes, assessments, Mello-Roos charges, and other direct charges can also appear on the same bill even though they are not all part of the Prop 13 rate.
The work is split among county offices. The assessor sets value and handles exemptions or exclusions. The auditor-controller calculates the tax. The tax collector mails the bill, takes payment, and handles delinquent accounts.
How it works
The numbers are related, but they are not the same
Market value is what a buyer may pay. Base-year value is the Prop 13 starting number. Factored base-year value is that number after allowed yearly increases. Taxable value is the number used for tax after an exemption or temporary market drop applies.
That is why a listing, an assessor page, and a tax bill may show different numbers. Each number has a different job.
For example, a $600,000 factored base-year value that gets the full 2 percent increase becomes $612,000. The basic 1 percent levy on that value is $6,120 before voter-approved debt and direct charges. A $7,000 homeowners' exemption would trim about $70 from that basic levy. It would not cut the bill by $7,000.
A sale or completed project can create a second bill
A change in ownership or finished construction can trigger a supplemental assessment. This starts the new value before the next annual roll. The assessor compares the new value with the old value. The county taxes the difference for the months left in the fiscal year.
The event date can lead to one or two supplemental bills. A lower new value can lead to a refund instead.
Temporary market drops can move faster than 2 percent
When market value falls below the Prop 13 track, Proposition 8 can lower the taxable value for a while. The assessor checks it each year. As the market recovers, that temporary value can rise by more than 2 percent. It still cannot pass the Prop 13 track unless a new reassessment event occurs.
Relief usually starts with a county claim
The homeowners' exemption can lower the taxable value of a qualifying owner-occupied home by up to $7,000. It does not cut the bill by $7,000. File the claim with the county assessor.
Proposition 19 has its own rules for some base-year transfers and family transfers. Occupancy, relationship, value, timing, and filing all matter. Use the state material and the assessor for the county where the home sits.
First moves
- 1
Find the parcel number and current assessed value on the county assessor's site.
- 2
Write down the event that may have changed the value: a purchase, inheritance, trust transfer, ownership change, addition, rebuild, or completed construction.
- 3
Keep the annual tax bill separate from any Notice of Supplemental Assessment. They cover different rolls and may arrive at different times.
- 4
Use the assessor for value, exemptions, exclusions, and reassessment. Use the tax collector for the bill, payment, and penalties.
- 5
For a transfer, estate, trust, or major project, confirm the treatment before relying on an estimate.
Watch for
- 1
A sale is not the only thing that can count as a change in ownership.
- 2
An exclusion from reassessment is not the same as an exemption from tax, and some relief requires a claim.
- 3
The 2 percent cap applies to the factored base-year value. It does not cap every line on the bill or a temporary Proposition 8 recovery.
- 4
Special assessments, bonds, Mello-Roos taxes, and direct charges can make the total higher than the basic 1 percent levy.
- 5
A supplemental bill is separate from the regular annual bill. Read the dates and parcel number on each notice.
Official sources
Where to confirm this
Use the source that matches the part you need. Current forms, fees, deadlines, maps, and local decisions can change after this guide is reviewed.
Property-tax treatment can turn on ownership structure, trust terms, occupancy, filing dates, exclusions, new construction, and county records. Use the county assessor for the parcel and qualified tax or legal help for a transfer or estate.