Property tax bills can feel like a puzzle, especially when you see line items you do not recognize. If you own a home in San Dimas or plan to buy or sell soon, understanding how Los Angeles County calculates and collects property taxes will help you avoid surprises. In this guide, you will learn how assessed values work, what shows up on your bill, key deadlines, how taxes are handled in a sale, and the relief programs that may lower your costs. Let’s dive in.
How San Dimas property taxes work
The 1% base rate and assessed value (Prop 13)
Under California’s Proposition 13, the base property tax rate is 1% of your assessed value. Your assessed value is tied to your purchase price, also called your base year value. As long as you keep the property and do not complete new construction, that value can rise by a maximum of 2% per year for inflation.
If you sell or complete new construction, the property is generally reassessed to current market value. That new value becomes the starting point for future annual increases limited by Prop 13.
Temporary reductions when values fall (Prop 8)
If market value drops below your Prop 13 base year value, you may receive a temporary reduction under Proposition 8. When market values recover, the Assessor can raise the assessed value back up, but not above what your Prop 13 value would have been with the allowed annual increases.
Portability and family transfers (Prop 19)
Proposition 19 changed two big areas. It limits some parent-child and grandparent-grandchild exclusions unless the property remains the family home and you meet certain conditions. It also expands portability for eligible homeowners age 55+, those who are severely disabled, or those who are victims of wildfire or disaster, allowing a transfer of your taxable value to a replacement primary residence anywhere in California, subject to program rules and timelines.
What appears on your Los Angeles County bill
Your total tax is more than the 1% base. In San Dimas, the bill commonly includes:
- The 1% base tax on assessed value under Prop 13.
- Voter‑approved bond charges for school districts and other local agencies.
- Special assessments and fees, such as lighting, landscaping, water, or sewer districts where applicable.
- Mello‑Roos or Community Facilities District (CFD) special taxes that apply to many newer subdivisions.
- Other parcel‑level assessments for local services.
Each parcel is different. To know the exact amount for a specific property, review the actual tax bill or contact the Los Angeles County Treasurer and Tax Collector.
Key dates and payment timeline
Annual cycle and due dates
California’s property tax fiscal year runs July 1 through June 30. Secured property taxes are paid in two installments each year:
- First installment: Due November 1, delinquent after December 10.
- Second installment: Due February 1, delinquent after April 10.
If a due date falls on a weekend or holiday, the county applies the next business day rule for delinquency. Payment options and specific instructions are available from the County Treasurer and Tax Collector.
Late payments and penalties
If you miss the delinquency date, penalties and interest begin to accrue, and continued nonpayment can lead to collection actions. If you run into trouble, contact the Los Angeles County Treasurer and Tax Collector to ask about relief options and procedures.
What to know about supplemental assessments
When ownership changes or new construction is completed, the county issues a supplemental assessment. This adjusts the prior assessed value to the new assessed value for the portion of the fiscal year that the change applies. The county sends a separate supplemental tax bill. It can arrive months after closing and often surprises new owners who only planned for the regular bill.
Supplemental assessments can be increases or, less often, decreases. Either way, treat any supplemental bill as separate from your regular installments and calendar it so you do not miss the due date.
Buying or selling: who pays what
Prorations at closing
In a typical San Dimas sale, the regular annual property taxes are prorated at closing. The seller pays taxes up to the day of closing. The buyer pays from closing through the end of the tax period. Your escrow instructions will spell this out.
Who handles supplemental taxes
Supplemental tax bills are usually issued to the owner of record at the time of reassessment, which is often the buyer. Many buyers and sellers negotiate credits in escrow to offset expected supplemental taxes, especially when the new assessed value will be much higher than the prior owner’s value. Always confirm responsibilities in your purchase contract and escrow instructions.
Tax relief and savings you may qualify for
Homeowners’ Exemption
If the property is your principal residence, apply for the Homeowners’ Exemption. This reduces your taxable assessed value by a statutory amount, commonly $7,000. The application is typically a one‑time filing. Check Los Angeles County instructions to confirm current amounts and deadlines.
Disabled veteran and other exemptions
California and Los Angeles County offer exemptions for certain situations, including disabled veterans. Programs vary by eligibility and benefit level. Review county guidance and submit any required forms by published deadlines.
Property Tax Postponement program
The State of California’s Property Tax Postponement (PTP) program may allow qualified seniors age 62 or older, or blind or disabled homeowners with limited incomes and sufficient equity, to postpone current‑year property taxes. The program is administered at the state level and operates like a deferral. Check current rules and application windows.
Prop 19 portability for a move
If you are 55+, severely disabled, or a victim of wildfire or disaster, you may transfer your taxable value to a replacement primary residence anywhere in California, subject to timing and value‑difference rules. File the required paperwork with the county assessor to claim the benefit. This can help you keep a lower assessed value even if your next home is in a different county.
If your assessed value seems too high
Start with the Assessor
If something looks off, contact the Los Angeles County Assessor first. Ask for a review of your record to confirm facts such as square footage, condition, exemptions, or completion dates for new construction. Clerical corrections can sometimes resolve issues without a formal appeal.
File a formal appeal if needed
If the value still appears incorrect, you can file with the Los Angeles County Assessment Appeals Board. Your petition must be submitted within the county’s published deadlines. Watch for your Notice of Assessed Value and follow the instructions to avoid missing the filing window.
What evidence helps
Strong evidence includes recent comparable sales, a qualified appraisal, documentation of income or costs for income properties, proof of construction status, and any records showing errors in the assessor’s data. Organize your materials clearly for the hearing.
Smart due‑diligence checklist for San Dimas
Buyers
- Ask the seller for the most recent property tax bill. Note the 1% base tax and any bond charges, special assessments, or Mello‑Roos.
- Review your preliminary title report and escrow instructions for assessments that may not be obvious.
- Discuss proration methods and whether the seller will provide a credit for expected supplemental taxes after reassessment.
- After closing, confirm your ownership information with the county so future regular and supplemental bills are addressed correctly.
Sellers
- A sale triggers reassessment, which usually leads to supplemental tax bills. Consider negotiating escrow credits to account for the buyer’s likely supplemental liability.
- Provide the buyer with recent tax bills and disclose any special assessments.
Everyone
- Apply for the Homeowners’ Exemption if the property is your principal residence.
- If you plan to move and may qualify for Prop 19 portability, review the rules before closing so you can file the right forms on time.
- Keep copies of your grant deed, closing statement, and any correspondence from the county. These records help if you need to respond to a supplemental bill or file an appeal.
Common scenarios to expect
- You buy a San Dimas home that was long held by the prior owner. Your assessed value resets to the new purchase price, so your future tax bill will likely be higher than the seller’s prior bill.
- You complete a major remodel or addition. Once the county determines completion, it may issue a supplemental assessment for the new construction value.
- The market dips below your base year value. The Assessor may apply a temporary Prop 8 reduction. If the market rebounds, your assessed value can rise more than 2% in a year until it returns to your Prop 13 trended level.
Bottom line for San Dimas homeowners
Understanding the 1% base rate, local add‑ons, due dates, and supplemental assessments will help you plan your budget and avoid penalties. When you buy or sell, align your escrow prorations and credits with how Los Angeles County bills and reassesses properties. If you qualify for exemptions or portability, file early so you do not miss out on savings.
If you want help estimating taxes on a purchase or sale, reviewing a bill, or planning escrow credits, reach out for local guidance. Connect with Shannon Brady to talk through your options or Get an Instant Home Valuation.
FAQs
How are San Dimas property taxes calculated?
- Your base tax is 1% of the assessed value under Proposition 13, plus voter‑approved bonds, special assessments, and any Mello‑Roos that apply to your parcel.
When are Los Angeles County property taxes due each year?
- The first installment is due November 1 and delinquent after December 10; the second is due February 1 and delinquent after April 10.
What is a supplemental property tax bill after I buy in San Dimas?
- It is a separate bill that adjusts taxes from the prior assessed value to your new assessed value for the part of the fiscal year after your purchase or new construction.
Who pays supplemental taxes in a San Dimas home sale?
- The county bills the owner of record when the reassessment occurs, often the buyer, though escrow credits for expected supplemental taxes can be negotiated.
Can I lower my assessed value if the market drops?
- Yes, under Proposition 8 the Assessor may grant a temporary reduction when market value is below your Prop 13 base year value, with future adjustments as the market changes.
