The Williamson Act: California's Farmland Property Tax Break
The Williamson Act (the California Land Conservation Act of 1965) lets owners of agricultural and open-space land agree to keep it in farming use in exchange for a lower property tax. The county assesses the land on its restricted farming value — what it can earn in agriculture — instead of full market value, which commonly cuts the tax bill 20–75%. Roughly half of California's farm and ranch land is enrolled.
How it works
You sign a contract with your county (or city) agreeing to restrict the land to agricultural or compatible open-space use for a minimum of 10 years. The contract renews automatically every year, so it always has about a decade left running unless you file to end it. While it's in force, the assessor values the land differently — and that's where the tax saving comes from.
The three values — and why the bill drops
Each year the assessor compares three values and taxes the land on the lowest:
- Restricted (Williamson) value — capitalized agricultural income.
- Proposition 13 factored base-year value — your Prop 13 value.
- Current market value.
On enrolled land the restricted value is usually the lowest, so that's what's used — often far below what the land would fetch on the open market.
Who qualifies
Land in commercial agriculture or qualifying open-space use that meets your county's size and use standards. Counties set their own thresholds — commonly around 10 acres of prime farmland or 40 acres of non-prime or grazing land, though this varies. It is meant for working farms, ranches, and open space, not an ordinary residential lot. You apply through the county planning department or assessor, and the parcel must be inside a designated Agricultural Preserve.
Farmland Security Zones (the “Super” Williamson Act)
A Farmland Security Zone contract is a 20-year version. In exchange for the longer commitment, the land is assessed at an even lower restricted value — often about 35% below the standard Williamson restricted value — for a deeper property-tax reduction. Availability depends on the county.
Getting out: non-renewal vs. cancellation
- Non-renewal — you file a notice and the contract stops renewing, winding down over the remaining ~9-year term while the assessment gradually climbs back to market value. No penalty.
- Cancellation — you end it immediately, but you generally must meet strict legal findings and pay a fee of about 12.5% of the land's current unrestricted market value. Because that's expensive, most owners who want out choose non-renewal.
Things to weigh
The trade-off for the tax break is a real, long-term use restriction: you commit to keeping the land in agriculture or open space, which limits development and can affect resale and financing. The savings are largest where market value far exceeds farming value, and small where they're close. A home and its home site on the parcel are assessed separately at their normal Proposition 13 value — the reduction applies to the land in agricultural use.
Frequently Asked Questions
What is the Williamson Act in California?
The Williamson Act — formally the California Land Conservation Act of 1965 — lets a landowner sign a contract with their county (or city) agreeing to keep land in agricultural or compatible open-space use for at least 10 years. In exchange, the county assesses the land on its restricted farming value rather than its full market value, which usually lowers the property tax substantially. The contract renews automatically each year, so it always has about 10 years left unless someone files to end it.
How much does the Williamson Act save on property taxes?
It varies widely by parcel, but savings commonly run from about 20% to 75% of the property tax bill. The saving comes from how the land is valued: instead of market value, the assessor uses a 'restricted' value based on the income the land can produce in agriculture (capitalized farming income). On land where the market value is far above its farming value — for example, ranch land near growing suburbs — the reduction can be large. Where farming value and market value are close, the saving is small.
How is the assessed value calculated under a Williamson Act contract?
The assessor compares three values and taxes the land on the lowest: (1) the restricted 'Williamson' value from capitalized agricultural income, (2) the Proposition 13 factored base-year value, and (3) the current market value. On enrolled land the restricted value is usually the lowest, so that's what's used — which is why the bill drops.
Who qualifies for the Williamson Act?
Land devoted to commercial agriculture or qualifying open-space use, meeting your county's minimum size and use standards. Counties set their own rules — commonly around 10 acres of prime farmland or 40 acres of non-prime/grazing land, though the thresholds vary. It is not for a typical residential home lot; it's aimed at working farms, ranches, and open space. Check your county's Agricultural Preserve rules and apply through the county planning department or assessor.
What is a Farmland Security Zone (Super Williamson Act)?
A Farmland Security Zone contract is a 20-year version of the Williamson Act. In return for the longer commitment, the land is assessed at an even lower restricted value — often about 35% below the standard Williamson Act restricted value — for a further property-tax reduction. Not every county offers them.
How do I get out of a Williamson Act contract?
Two ways. Non-renewal: you file a notice and the contract stops auto-renewing, winding down over the remaining ~9-year term as the assessment gradually returns to market value — no penalty. Cancellation: you end it immediately, but you generally must show it meets strict legal findings and pay a cancellation fee of about 12.5% of the land's current unrestricted market value. Because cancellation is costly, most owners who want out use non-renewal.
Does the Williamson Act affect the house on the land?
The contract restricts and values the agricultural land. A residence and its home site on the parcel are generally assessed separately at their normal Proposition 13 value — the reduced valuation applies to the farmed/open-space land, not the house.
Learn More
Educational overview, not legal or tax advice. The Williamson Act is administered by counties, and eligibility rules, minimum acreage, and available programs vary — confirm specifics with your California Department of Conservation and county assessor / planning department before acting. General property-tax rules: California BOE.