Property Tax

Prop 13 tax reset estimator

Get a rough heads-up on how a purchase can reset the tax bill and cause a later supplemental bill.

Calculator Last reviewed June 29, 2026

Why it matters

It is easy to see the seller's old tax bill and think yours stays the same. It often does not. After many sales, the county assessor can set a new value. A supplemental bill may come later.

Directory shelf

Home costs

Property tax, closing costs, Mello-Roos, and surprise bills.

Open official source Browse this shelf

Calculator

Rough tax reset

This is a rough estimate, not a tax bill. The county assessor and tax collector control the real value, tax rate, exemptions, add-on charges, proration, and bill.

First moves

1
Type in the purchase price or new value.
2
Type in the seller's current assessed value if you know it.
3
Pick the month the sale or other reset happened.
4
Use the county's real tax rate if you have it. If not, start with 1.1 percent.
5
Treat the answer like a warning light. Then check the county assessor and tax collector.

Watch for

1
Prop 13's 1 percent idea is only the starting point. Local debt, special taxes, Mello-Roos, and direct charges can add more.
2
A January to May reset can make two supplemental bills. June to December usually makes one.
3
If the new value is lower than the old value, the math can point to a refund instead of a bill.
4
The real bill depends on the date, county timing, exemptions, and assessed value.
5
A low old tax bill can reset sharply after a sale.
6
This is not a county bill and not a substitute for escrow, assessor, or tax-collector numbers.

Go deeper

Prop 13 and California property tax basics

A simple starting point for base-year value, the 1 percent tax limit, reassessment, and why your county assessor matters.

Directory paths

Keep moving through the directory.

Use the nearby shelf when this is the right lane, or jump back to the full directory if the task changed names.

ShelfHome costsProperty tax, closing costs, Mello-Roos, and surprise bills.DirectoryPaperwork & MoneyReturn to the full tools shelf.Nearby toolTransfer tax estimatorGet a rough transfer-tax number before escrow gives you the official closing statement.Nearby toolMello-Roos tax checkA plain checklist for spotting Mello-Roos, CFDs, parcel taxes, and other add-on lines before you buy.A-ZFind another California pathUse the directory index when the task has a different name.