California Prop 13 Property Tax Guide
Proposition 13 holds California property taxes to roughly 1% of assessed value plus voter-approved debt, with annual assessed-value increases capped at 2% until the property changes hands or gets new construction. On an $850,000 Orange County purchase, expect about $9,350 to $10,200 per year in base property tax, before Mello-Roos or HOA dues. Neighbors in identical houses can pay wildly different taxes based on when each bought. This guide covers the rate, the cap, the reassessment triggers, the supplemental bills that surprise new buyers, and how appeals work. Cost information only, not tax advice.
Orange County, CA · Updated 2026 · Costs shown as ranges — your quote will vary by contractor and scope
The 1% base and the 2% cap
Proposition 13 (1978) sets the statewide base at 1% of assessed value, plus voter-approved local debt (bonds, parcel taxes) that typically adds 0.1% to 0.3% in Orange County, for an effective rate around 1.1% to 1.25%. The famous part is the cap: your assessed value can rise at most 2% per year, no matter how fast market values climb. Buy a home for $850,000 and ten years later it is worth $1.3M; your assessed value is at most about $1,037,000, and your tax reflects that, not the market price.
The cap compounds quietly into enormous differences. A homeowner who bought in 1995 for $250,000 pays tax on roughly $450,000 of assessed value today; their 2026 buyer next door pays on the full $1.2M purchase price. Same street, triple the tax: predictable for long-term owners, with the trade-off landing on movers. Understand which side of that trade you are on before you buy.
When your home gets reassessed
Two triggers reset assessed value to market: a change in ownership (your purchase) and new construction (the addition, not the whole house, gets added at market value). Remodels without added square footage, market appreciation, and refinancing do not trigger reassessment. The assessor sets the new base year value from your purchase price, and the 2% cap starts ticking from there.
Proposition 19 (2021) rewrote the family-transfer rules. Now a parent-to-child transfer keeps the low assessment only if the child makes it their primary residence. Intergenerational transfers need current professional advice. Some trust and entity transfers can trigger reassessment; ask the assessor before you transfer, not after.
Supplemental bills: the surprise after closing
Here is the surprise that hits nearly every California buyer: the supplemental tax bill. Your regular tax bill reflects the seller's old assessed value until the assessor processes your purchase. The supplemental bill covers the difference between the old assessed value and your purchase price, prorated from your closing date to the next tax year. On an $850,000 purchase replacing a $400,000 assessment, expect $4,000 to $5,000, arriving months after closing.
Budget for it from day one: set aside roughly 1.1% of the assessment increase, prorated. It comes in two installments, is really owed, and delinquency triggers penalties. Lenders do not impound for supplementals, so this one comes out of pocket. It is in the fine print; now you have read it.
Appealing your assessment
If your assessed value exceeds market value, you can appeal to the county Assessment Appeals Board. Realistic cases: you bought at the peak and values fell, or the records are wrong. File during the county window (OC: July 2-November 30) with comparable sales from the lien date (January 1).
Two honest notes. Appeals on recently purchased homes rarely succeed: your purchase price is the board's best comp. The informal route often works better: a Proposition 8 review call with good comps sometimes gets a reduction without a hearing. Never pay a contingency-fee mill 40% of savings before checking whether you could file yourself.
Prop 13 mechanics at a glance, Orange County (2026)
| Element | Rule of thumb |
|---|---|
| Base rate | 1% of assessed value |
| Typical effective rate (OC) | ~1.1% – 1.25% with voter debt |
| Annual increase cap | 2% of assessed value |
| Reassessment triggers | Change of ownership; new construction |
| $850,000 purchase, base tax | ~$9,350 – $10,200 / yr |
| Supplemental bill (example) | ~$4,000 – $5,000 on $450k assessment jump |
| Appeal filing window (OC) | July 2 – November 30 |
| Prop 19 family transfers | Primary-residence requirement now applies |
DIY vs. hiring a pro
DIY your Prop 13 position once a year: check the assessor's site for your assessed value, compare it to a rough market value from recent nearby sales, and confirm the 2% cap was applied correctly. If you added square footage, verify only the addition was enrolled at market value, not the whole house. If market value has fallen below assessed value, run the appeal math: the filing is cheap, the window is July-November, and the Proposition 8 informal review costs nothing to ask about. And the single most valuable DIY move: budget the supplemental bill before closing, not after it arrives.
What drives the price up or down
- Purchase price -- sets your base-year value on day one
- Hold duration -- the 2% cap compounds for long owners
- Voter debt -- bonds and parcel taxes stack on the 1%
- New construction -- additions enroll at market value
- Prop 19 -- narrowed family-transfer exclusions
- Market cycles -- falling markets create appeal opportunities
How to keep the cost down
- Budget the supplemental bill before closing -- ~1.1% of the assessment jump
- Verify only new construction (not the whole house) got reassessed
- Check your assessed value yearly against market comps
- Use the free Proposition 8 review before paying for a formal appeal
- Get transfer advice BEFORE moving property between family members
- Remember: your purchase price is the board's best comp -- recent buyers rarely win appeals
Frequently asked questions
How is California property tax calculated?
Roughly 1% of assessed value plus voter-approved local debt (typically 0.1-0.3% more in OC). Assessed value starts at your purchase price and can rise at most 2% per year until a reassessment trigger.
When does Prop 13 reassessment happen?
On change of ownership and on new construction. Market appreciation, remodels without added square footage, and refinancing do not trigger reassessment.
What is a supplemental property tax bill?
A catch-up bill for the difference between the seller's old assessed value and your purchase price, prorated from closing. Budget ~1.1% of the assessment increase; it arrives months after closing and is not impounded.
Can I appeal my property tax assessment in California?
Yes, through the county Assessment Appeals Board (OC filing window: July 2-November 30). Best cases: falling markets where value dropped below assessment, or factual errors in the assessor's records. Try the free Proposition 8 review first.
Did Prop 19 change parent-to-child transfers?
Yes. The old unlimited exclusion is gone: the child must make it their primary residence to keep the parent's assessment (with partial adjustment above $1M over assessed value). Get professional advice before transferring property between family members.