Let's get the most important fact on the table first, because the internet gets it wrong surprisingly often: Simi Valley is in Ventura County, California — not Los Angeles County. Your property taxes are assessed by the Ventura County Assessor, collected by the Ventura County Treasurer-Tax Collector, and governed by the same Prop 13 rules as the rest of the state: a 1% base rate plus local voter-approved bonds, which puts most Simi Valley homeowners at a typical effective rate of roughly 1.1% to 1.2% of assessed value.
Why the county matters (and why so many sites get it wrong)
Simi Valley sits at the eastern edge of Ventura County, sharing a border with Los Angeles County at the Santa Susana Pass — Chatsworth and the West San Fernando Valley are just over the hill. Because of that geography, and because many Simi Valley residents commute into L.A., some national data-aggregator websites file Simi Valley under Los Angeles County, sometimes with property value figures far above what homes here actually sell for.
For a homeowner or buyer, the distinction is not academic:
Different assessor. Your assessed value, exemptions, and reassessment appeals all go through the Ventura County Assessor — (805) 654-2181, assessor.countyofventura.org — not the Los Angeles County Assessor's office. Different tax collector. Your bill comes from, and is paid to, the Ventura County Treasurer-Tax Collector. Different bonds. The line items on a Simi Valley bill are Ventura County and Simi Valley-area obligations — think Simi Valley Unified School District bonds and local district assessments — not L.A. County Metro or LAUSD measures. And different values: compiled regional MLS data puts the Simi Valley median sale price at about $836,000 (site compiled, June 2026). If a website shows you a "Simi Valley" median assessed or market value dramatically higher than that, it is blending in data from somewhere else.
How the tax is calculated: Prop 13 in plain English
California property tax runs on Proposition 13 (1978). Three rules do most of the work:
1. The base rate is 1%. The general levy is capped at 1% of your property's assessed value — not its current market value.
2. Assessed value is set at purchase, then capped. When you buy, the assessed value resets to your purchase price. After that, it can rise no more than 2% per year (plus the value of any new construction), no matter what the market does. This is why a neighbor who bought in 2004 can pay a fraction of what a 2026 buyer pays on an identical floor plan.
3. Voter-approved debt is added on top. School bonds and other voter-approved obligations are layered onto the 1% base as additional percentage rates, and fixed-dollar direct assessments (vector control, flood, lighting districts, and similar) are added as line items. In Simi Valley, these additions typically bring the total effective rate to about 1.1% to 1.2% of assessed value, varying slightly by tax rate area within the city — published parcel-record analyses put the citywide median effective rate right in this band (roughly 1.2%), consistent with the 1.1-1.3% norm across Ventura County.
Worked example: taxes on a median-priced Simi Valley home
The numbers below are illustrative only. They assume a purchase at the compiled June 2026 median sale price and a typical effective rate; your actual bill depends on your price, your tax rate area, and your parcel's direct assessments.
| Line | Rate | Annual Amount |
|---|---|---|
| Purchase price (= new assessed value) | — | $836,000 |
| Prop 13 base levy | 1.0% | $8,975 |
| Typical total with bonds/assessments — low end | ~1.1% | ~$9,870 |
| Typical total with bonds/assessments — high end | ~1.2% | ~$10,770 |
| Approximate monthly (escrowed) | — | ~$825-$900/mo |
Illustrative example based on the site-compiled June 2026 median of $836,000 and a typical 1.1-1.2% effective rate. Not a quote, an assessment, or tax advice.
Also budget for the Homeowners' Exemption: if the home is your primary residence, filing a one-time claim with the Ventura County Assessor knocks $7,000 off your assessed value — worth about $70 per year. Small, but it is free money and most escrow packets include the form.
How to check the exact tax on any Simi Valley parcel
Never rely on a listing site's "est. taxes" line — check the county's own records. Two steps:
Step 1 — Assessor lookup. Go to assessor.countyofventura.org and search by address or APN to see the current assessed value and property characteristics. (Questions: (805) 654-2181.)
Step 2 — Tax Collector bill. The Ventura County Treasurer-Tax Collector's site shows the actual current bill for that parcel, itemized: the 1% levy, each voter-approved bond rate, and every fixed direct assessment. This is the only place you will see the true all-in number, and it is exactly what I pull for clients during escrow. Remember when buying: the current owner's bill reflects their assessed value, not yours. Your bill will be based on your purchase price — use the rate structure from the bill, applied to your price.
The supplemental tax bill: the one that surprises new buyers
When you buy a Simi Valley home, the Ventura County Assessor reassesses it from the seller's old (often much lower) assessed value up to your purchase price. The regular tax bill for that fiscal year was calculated on the old value, so the county sends a supplemental tax bill for the difference, prorated from your closing date to the end of the fiscal year. Close between January and May and you may receive two supplemental bills covering both the current and upcoming fiscal years.
Two things catch people out. First, timing: the supplemental bill often arrives several months after closing, when the moving boxes are long gone. Second, escrow: supplemental bills are generally not paid by your lender's impound account — they come straight to you. On a home whose assessed value steps up from, say, $400,000 to $836,000, the supplemental amount is real money, so set aside for it. Details are on the Ventura County Treasurer-Tax Collector's supplemental tax page.
Mello-Roos in Simi Valley: mostly a non-issue
Good news for buyers comparing Simi Valley to newer master-planned areas: Mello-Roos (Community Facilities District) taxes are rare here. Most of Simi Valley's housing stock was built in the 1960s-1980s, before Mello-Roos financing (created in 1982) became standard for new communities — so the large majority of established tracts carry no Mello-Roos at all. A limited number of newer developments do carry CFD or similar special assessments, which is one reason an identical-looking bill can differ between tracts. This is a genuine cost advantage over places like Porter Ranch or parts of Santa Clarita, where Mello-Roos can add hundreds per month; see our no-Mello-Roos home directory and tract-by-tract lookup. Always verify the specific parcel's bill — it takes two minutes and removes all doubt.
Prop 19: bringing your old tax base with you
Proposition 19 (effective 2021) matters to two groups of Simi Valley buyers and owners:
Movers 55+ (and severely disabled or disaster-displaced owners). You can transfer your existing low assessed value from your current California primary residence to a replacement primary residence anywhere in the state — including into or out of Simi Valley — up to three times. If the replacement home costs more than the old one sold for, the difference is added to your transferred base. Example: sell a long-held home for $1,000,000 with a $350,000 assessed value, buy in Simi Valley for $1,100,000, and your new assessed value is roughly $350,000 + $100,000 = $450,000 — a tax bill of roughly half what a regular buyer at the same price would pay. Claims are filed with the Ventura County Assessor.
Heirs. Prop 19 also narrowed the old parent-child exclusion: an inherited home now keeps its low assessed value only if a child moves in as their primary residence within one year, and even then the exclusion is capped. Inherited rentals and second homes are generally reassessed to market value. If you are inheriting Simi Valley property, talk to the Assessor's office and a tax professional early.
Frequently Asked Questions
Is Simi Valley in Los Angeles County or Ventura County?
Simi Valley is entirely within Ventura County. Its property taxes are assessed by the Ventura County Assessor and collected by the Ventura County Treasurer-Tax Collector. It borders Los Angeles County to the east, and some data websites misfile it under Los Angeles County, but no Simi Valley address pays Los Angeles County property taxes.
What is the property tax rate in Simi Valley in 2026?
The base rate is 1% of assessed value under California's Proposition 13. Voter-approved bonds and direct assessments bring the typical total effective rate in Simi Valley to roughly 1.1% to 1.2% of assessed value, varying slightly by tax rate area. Check your exact parcel with the Ventura County Assessor.
How much is property tax on a median-priced Simi Valley home?
Using the site-compiled June 2026 median of about $836,000 as an illustrative purchase price: the 1% base is about $8,975 per year, and at a typical 1.1-1.2% effective rate the total is roughly $9,900 to $10,800 per year, or about $825 to $900 per month. Your actual bill depends on your purchase price and your parcel's tax rate area.
How do I look up the exact property tax on a Simi Valley home?
Use the Ventura County Assessor's property lookup at assessor.countyofventura.org (also reachable via assessor.venturacounty.gov) with the address or Assessor's Parcel Number (APN), or call (805) 654-2181. The Ventura County Treasurer-Tax Collector site shows the actual bill, including every bond and direct assessment for that parcel.
What is a supplemental tax bill in Ventura County?
When you buy a home (or complete new construction), Ventura County reassesses the property to its new market value. The supplemental bill covers the difference between the seller's old assessed value and your new one, prorated from your closing date. It arrives separately from the regular bill, often months after closing, and is not usually paid through your lender's impound account.
Does Simi Valley have Mello-Roos taxes?
Rarely. Most of Simi Valley's established neighborhoods were built before Mello-Roos (1982) became common, so the large majority of tracts have none. A limited number of newer developments carry community facilities district assessments, so always check the specific parcel's bill before you buy.
Can I transfer my low property tax base to a Simi Valley home under Prop 19?
Often, yes. Proposition 19 lets homeowners who are 55 or older, severely disabled, or wildfire/disaster victims transfer their existing assessed value to a replacement primary residence anywhere in California, up to three times. If the new home costs more than the old one sold for, the difference is added to the transferred base. File the claim with the Ventura County Assessor.
Why do some websites show Simi Valley property values far higher than the actual median?
Some aggregator sites misclassify Simi Valley's county and blend in data from other areas, which can produce inflated value and tax figures. Compiled MLS data puts the Simi Valley median sale price near $836,000 as of June 2026, and the taxing authority is the Ventura County Assessor. When in doubt, verify against the county's own records.
Related reading
- Simi Valley real estate overview
- Simi Valley property tax & Mello-Roos calculator
- Ventura County market report — August 2026
- Market data hub
- City guides
Sources: Ventura County Assessor (assessor.countyofventura.org / assessor.venturacounty.gov, (805) 654-2181); Ventura County Treasurer-Tax Collector (supplemental tax and collection FAQs, venturacounty.gov/ttc); California State Board of Equalization (Proposition 13 and Proposition 19 guidance, boe.ca.gov); California Association of REALTORS® (CAR). Median sale price: compiled regional MLS data, as of June 2026, checked against public portals August 2026. Published 2026-08-13.
Brian Cooper is a REALTOR® (DRE# 01434286), not a CPA, tax attorney, or enrolled agent. This guide is general information, not tax or legal advice — property tax outcomes depend on your specific parcel, exemptions, and filings. Verify figures with the Ventura County Assessor and consult a qualified tax professional for your situation. Equal Housing Opportunity.
