California Proposition 13 Explained
Proposition 13 fundamentally changed how California property taxes are calculated. Instead of basing taxes on a home's current market value every year, Proposition 13 generally ties a property's taxable value to the price paid when it was acquired, with limited annual inflation adjustments.
Understanding Proposition 13 helps explain why two nearly identical homes on the same street can have dramatically different property tax bills.
This guide explains how Proposition 13 works, when reassessment occurs, and how it affects homeowners, buyers, and investors.
What Is Proposition 13?
Proposition 13 is an amendment to the California Constitution approved by voters in 1978.
Before Proposition 13, many properties were regularly reassessed to current market value. During periods of rapidly increasing home prices, property taxes also increased substantially.
Proposition 13 introduced three major changes:
- It generally limits the general property tax rate to 1% of assessed value, excluding certain voter-approved indebtedness.
- It establishes a property's base-year value, commonly based on its acquisition value when ownership changes.
- It limits annual increases to the property's factored base-year value by the California inflation factor, capped at 2% per year, unless another reassessment event occurs.
These rules continue to form the foundation of California's property tax system today.
The Three Core Ideas
1. Base-Year Value
When a property changes ownership, the county assessor generally determines a new base-year value based on the property's fair market value at the time of transfer. In many arm's-length sales, the purchase price is strong evidence of that value.
Example
- Purchase date
- June 2018
- Purchase price
- $800,000
- Estimated base-year value
- $800,000
2. Annual Inflation Adjustment
After the base-year value is established, it generally increases each assessment year by the official California inflation factor. Over time, these annual adjustments create the property's factored base-year value.
The adjustment:
- uses the California Consumer Price Index,
- cannot exceed 2%,
- may be lower than 2%.
| Assessment year | Official increase |
|---|---|
| 2020-21 | 2.000% |
| 2021-22 | 1.036% |
| 2022-23 | 2.000% |
| 2023-24 | 2.000% |
3. Property Taxes
The property's assessed value is then used to calculate value-based property taxes. The total bill generally includes:
- the constitutional 1% general levy,
- applicable voter-approved debt rates,
- and may also include parcel-specific direct charges that are not based on assessed value.
Our California Property Tax Calculator estimates this process using historical Proposition 13 inflation factors and county-level estimated tax rates.
How to calculate the taxable value of your home
Under Proposition 13, the taxable value (also called the assessed or factored base-year value) is what your property tax is actually charged on — not your home's current market value. You can work it out in three steps:
- Start with the base-year value — the market value when you bought the home or completed new construction (for most owners, the purchase price).
- Apply the annual inflation factor for each year since — capped at 2% a year. Multiply the base value by the compounded factors to get the factored base-year value.
- Subtract any exemptions — such as the $7,000 Homeowners' Exemption — to reach the net taxable value the tax rate is applied to.
| Step | Example |
|---|---|
| Base-year value (bought 2016) | $500,000 |
| After ~2%/yr to 2026 (about +22%) | ≈ $609,000 |
| Less Homeowners' Exemption | − $7,000 |
| Taxable value | ≈ $602,000 |
| Tax at ~1.1% | ≈ $6,600/yr |
If the market value falls below this figure, the assessor can lower your taxable value temporarily under Proposition 8. To skip the arithmetic, the California property tax calculator applies the official inflation factors for you.
Why Two Neighbors Pay Different Property Taxes
One of the most common questions about California property taxes is why neighboring homes often have very different tax bills.
| Home | Purchase year | Purchase price |
|---|---|---|
| Home A | 1998 | $300,000 |
| Home B | 2025 | $1,400,000 |
Even if both homes are worth approximately $1.5 million today, their assessed values may differ substantially because Proposition 13 generally follows each property's own acquisition history. As a result, longtime owners often pay significantly less in property taxes than recent buyers.
When Can a Property Be Reassessed?
A property's assessed value does not automatically reset to current market value every year. However, reassessment can occur when certain events happen. Common examples include:
- purchase of the property,
- many ownership transfers,
- certain inheritances that do not qualify for an exclusion,
- taxable new construction,
- completion of a major addition.
Each situation is governed by California law and may have important exceptions.
What Happens if Home Prices Fall?
Many people believe assessed values can never decrease. That is incorrect.
If a property's current market value falls below its normal Proposition 13 factored base-year value, the county assessor may temporarily reduce the enrolled taxable value under Proposition 8.
As the market recovers, the taxable value may increase by more than 2% until it reaches the normal Proposition 13 factored base-year value again.
Learn more in our Proposition 8 guide.
What Proposition 13 Does Not Do
Proposition 13 does not mean:
- every homeowner pays exactly 1%,
- taxes can never increase by more than 2%,
- market value is ignored forever,
- reassessment never occurs,
- all taxes are capped at 1%.
Many California property tax bills also include:
- voter-approved bonded indebtedness,
- parcel taxes,
- Mello-Roos special taxes,
- special assessments,
- supplemental assessments after certain events.
Common Misconceptions
“Property taxes are always 1%.”
Not necessarily. The constitutional general levy is generally 1% of assessed value, but additional voter-approved ad valorem taxes and direct assessments may increase the total property tax bill.
“My taxes can never increase by more than 2%.”
Not always. While Proposition 13 generally limits annual increases in the factored base-year value, Proposition 8 restorations and certain reassessment events can result in larger increases.
“Current market value determines my taxes.”
Usually not for existing owners. Under Proposition 13, assessed value generally follows the property's acquisition history rather than current market value.
Frequently Asked Questions
How much can property taxes go up in a year in California?
For an existing owner, Proposition 13 caps the annual increase in a property's taxable (factored base-year) value at 2% — and the official inflation factor is sometimes less than 2%. So the value-based portion of your tax normally rises no more than about 2% a year. It can go up more in specific cases: when the market recovers a prior Proposition 8 reduction, when a reassessment event happens (a sale, ownership change, or new construction), or when voters approve new bonds or parcel taxes that are added on top.
Can my property tax increase by more than 2%?
Yes. The 2% limit applies to annual growth of the factored base-year value for an unchanged property. A reassessment event (purchase, many ownership transfers, or taxable new construction) can reset the value to market, a Proposition 8 recovery can restore value by more than 2% until it reaches the normal Prop 13 value, and new voter-approved debt or parcel taxes can raise the total bill independently of the 2% cap.
What is a factored base-year value?
It is the property's original base-year value adjusted each year using California's official Proposition 13 inflation factors.
Is assessed value the same as market value?
No. Market value estimates what the property could sell for today. Assessed value is used to calculate property taxes.
Why do recent buyers pay higher taxes?
Because a purchase commonly establishes a new base-year value based on current market conditions.
Does Proposition 13 apply to rental property?
Generally, yes. Proposition 13 applies to most real property regardless of whether it is owner-occupied or rented, although different rules may apply in certain situations.
Does remodeling trigger reassessment?
Some types of taxable new construction can create a new assessed value for the improvements while leaving the existing property's base-year value intact.
Learn More
This guide is intended for educational purposes and provides a general overview of California property tax rules. Property taxation is governed by the California Constitution, the Revenue and Taxation Code, and county assessor practices. Individual circumstances may produce different results. For legal or tax advice, consult a qualified professional or the appropriate county assessor.