Downsizing in Mission Viejo in 2026: The Prop 19 Math on Moving to Casta del Sol or Palmia

Quick answer: Often, yes. If you are 55 or older when you sell your Mission Viejo principal residence and buy or build your next one within 2 years, Prop 19 lets you carry its taxable value anywhere in California, up to 3 times (California BOE). CRMLS medians, 12 months to Oct 18, 2026: Casta del Sol $895,500, Palmia $1,025,000, citywide $1,215,000.

By Darren Shepherd, Mission Viejo real estate agent, CA DRE #02000042, The Darren Shepherd Team at Compass California, Inc.

Moving from a larger Mission Viejo house into Casta del Sol or Palmia can lower your property tax bill instead of raising it, if the Prop 19 numbers line up. Darren Shepherd, a Mission Viejo neighborhood specialist on The Darren Shepherd Team at Compass California, Inc., wrote this guide to run that math with 12 months of CRMLS closed sales for the city and both communities.

This guide is a worked Mission Viejo calculation, not a general overview of the law. Nothing here is tax or legal advice. Talk to a CPA or tax advisor about your situation before you decide.

Can you keep your low property tax if you downsize within Mission Viejo?

3 times: that is how often a homeowner who is at least 55 can move the taxable value of a principal residence to a replacement home under Prop 19, and the replacement can be anywhere in California at any value (California Constitution, article XIII A, section 2.1; California State Board of Equalization, Prop 19). The rule took effect April 1, 2021, and is implemented by Revenue and Taxation Code section 69.6.

The core conditions, from the BOE and the Orange County Assessor's Transferring Base Year Value page:

• The home you sell must be your principal residence, eligible for the homeowners' or disabled veterans' exemption, at the time of sale or within 2 years of buying the replacement.
• The age test applies on the date the original home sells. Severely and permanently disabled owners and wildfire or disaster victims qualify under the same section without the age requirement.
• The replacement must be bought or built within 2 years before or after that sale, and it must be your principal residence when you file.
• Each person can use the age or disability transfer 3 times, so a married couple can potentially use it 6 times, 3 for each spouse (BOE Letter to Assessors 2024/044).

For a move within Mission Viejo, the claim goes to the Orange County Assessor.

What do Casta del Sol and Palmia homes sell for compared with the rest of Mission Viejo?

$895,500 in Casta del Sol and $1,025,000 in Palmia: those were the median sale prices of closed sales, every home type combined, from Oct 19, 2025 to Oct 18, 2026, against $1,215,000 for Mission Viejo as a whole (CRMLS).

• Mission Viejo, citywide: 958 sales, median $1,215,000, $649 per square foot, 17 median days on market.
• Casta del Sol: 116 sales (115 single-family), median $895,500, $650 per square foot, 32.5 median days on market.
• Palmia: 47 sales, median $1,025,000, $612 per square foot, 13 median days on market. Its 29 single-family sales had a $1,189,000 median and its 18 condominium sales $790,000.

The gap between the city median and Casta del Sol's is $319,500. The gap to Palmia is $190,000.

Both are 55+ communities. Casta del Sol's homeowners association describes it as a 55+ community (Casta del Sol Community HOA), and Palmia's calls it an "active 55 and better lifestyle community" of 639 single-family homes and 262 condominiums (Palmia HOA). For 12 months of closed Casta del Sol sales, see our Casta del Sol home values report. Medians are not prices for one home.

What is the Prop 19 math on a move from a $1.215 million Mission Viejo home?

$4,000 a year in 1% base tax instead of $8,955: that is the illustration for a seller with a $400,000 Prop 13 value who sells at the $1,215,000 citywide median and buys at Casta del Sol's $895,500 median. The $400,000 is an example input, not a market figure. Your own is the assessed value on your Orange County tax bill.

Here is the arithmetic, using the BOE's equal-or-lesser value test and the OC Treasurer-Tax Collector's 1% base rate (OC property tax guide):

• Step 1, the value test. Buying within the first year after the sale, the limit is 105% of the original home's value: $1,215,000 x 1.05 = $1,275,750.
• Step 2, compare. $895,500 is below that limit, so nothing is added. The replacement takes the $400,000 value.
• Step 3, the 1% base tax. $400,000 x 1% = $4,000 a year. Without a transfer, if the price becomes the assessed value, $895,500 x 1% = $8,955.
• Palmia, same steps. $1,025,000 is also below the limit, so the value stays $400,000. Without a transfer, $1,025,000 x 1% = $10,250, or $6,250 more a year.

These are 1% base figures only, before the homeowners' exemption ($7,000 in the OC guide's example) and any inflation adjustment the assessor applies. Voter-approved bonds, special assessments and any Mello-Roos are added on top, so check the replacement home's current bill by address on the OC Treasurer-Tax Collector site. For what Mission Viejo owners pay today, see our Mission Viejo property tax guide.

Does it matter whether you buy before or after you sell?

$65,000 versus $0: in this example, that is the difference timing makes. Prop 19 compares the replacement price with 100% of the original home's value if you buy first, 105% if you buy in the first year after the sale, and 110% in the second year (BOE Prop 19 FAQ). Anything above that line is added to your transferred value.

Take an illustrative $960,000 sale, a $400,000 Prop 13 value and a Palmia purchase at the $1,025,000 median:

• Buy before you sell (100%). $1,025,000 - $960,000 = $65,000 is added. New taxable value: $465,000, or $4,650 a year at 1%.
• Buy within a year after you sell (105%). The limit is $1,008,000, so $17,000 is added. New taxable value: $417,000, or $4,170 a year.
• Buy in the second year after you sell (110%). The limit is $1,056,000, so nothing is added. New taxable value: $400,000, or $4,000 a year.

Buying first has a second cost. The BOE says that if you buy the replacement before the original sells, you pay tax on the replacement's full fair market value until the sale, with no refund for that period. A contingent offer is one way to line up both closings; see how to sell and buy in one move in Mission Viejo.

Which forms and deadlines apply in Orange County?

3 years: that is how long you have to file form BOE-19-B (the age-55 form) with the assessor of the county where the replacement home sits, counted from the date you buy it or finish building it (BOE filing checklist; Revenue and Taxation Code section 69.6).

• When to file: after both sales have closed and you live in the replacement home. The BOE says the transfer is not done through escrow.
• Where: for a Casta del Sol or Palmia purchase, the Orange County Assessor. The OC Assessor forms page lists no filing fee for this form.
• If you file late: the BOE says relief starts with the year you file, with no refund for earlier years (BOE Letter to Assessors 2024/044).

What if you already used Prop 60 or Prop 90, or inherited the home?

0: that is how many of your 3 Prop 19 transfers a past Prop 60 or Prop 90 transfer uses up. The BOE says owners who are over 55 or disabled get 3 transfers under Prop 19 whether or not they transferred a base year value under the older rules (BOE Prop 19 FAQ).

• An inherited home can count as the original home if you own it and live in it as your principal residence at the time of sale, or within 2 years of buying the replacement, per the same BOE FAQ.
• Shared title on the new home does not block the claim. The BOE says the claimant does not have to be the sole owner, as long as all co-owners buy together and the claimant is one of them.

If you used Prop 60 or Prop 90 years ago, that door is not closed.

Should you run the Prop 19 numbers before you list?

1 date decides the age test: the day your current home sells, not the day you buy, so run the numbers before you list. Senior Communities is one of Darren Shepherd's two specialties, and a Prop 19 plan starts with the same two figures: the sale price and the closing date of the current home.

Run the Prop 19 numbers before you list if:

• You have owned your Mission Viejo home long enough that its assessed value is far below today's prices.
• You will be at least 55 by the expected closing date.
• You are choosing between buying first and selling first.
• You have used the transfer before and want to count how many uses remain.

Look first at Casta del Sol if: your target price is closer to its $895,500 median and you want a single-family home.

Look first at Palmia if: you want a choice between single-family homes and condominiums inside one association, near its $1,025,000 median.

Ask each association for its current age and occupancy rules. Homes for sale right now are in our Mission Viejo home search. If you'd rather have a one-level home elsewhere in the city, read downsizing to a single-story home in Mission Viejo.

What this guide does not cover: capital gains tax on the sale, parent-to-child transfers, trusts, moves to another county's tax rates, Mello-Roos on a specific address, and HOA dues. Ask me about any of them, and talk to a CPA or tax advisor about your situation before you decide.

Sources, each checked on Oct 23, 2026: California Constitution, article XIII A, section 2.1; Revenue and Taxation Code section 69.6; California State Board of Equalization, Prop 19 page, FAQ and filing checklist, and Letter to Assessors 2024/044; Orange County Assessor, Transferring Base Year Value and forms pages; OC Treasurer-Tax Collector, Property Tax Guide for New Homeowners; CRMLS closed sales, all home types, Oct 19, 2025 to Oct 18, 2026; Casta del Sol Community HOA and Palmia HOA websites. The $400,000 Prop 13 value and the $960,000 sale are illustrations.

Frequently Asked Questions

Can I transfer my property tax base if I downsize in Mission Viejo?

Yes, if you are at least 55 on the date your current home sells, it is your principal residence, and you buy or build a replacement principal residence within 2 years before or after that sale. Under Prop 19 the replacement can be anywhere in California, and each person can use the transfer up to 3 times, per the California State Board of Equalization.

Does Prop 19 work if my new home costs more than my old one?

Yes. Depending on timing, none, some or all of the price difference is added. If the new home costs more than 100% of the old home's value (bought before the sale), 105% (within a year after) or 110% (in the second year after), the amount above that line is added to your transferred value, per the BOE.

How do I file for a Prop 19 base year transfer in Orange County?

If you qualify by age, file form BOE-19-B (disabled owners use BOE-19-D, disaster victims BOE-19-V) with the Orange County Assessor after both sales close and you live in the new home, within 3 years of buying it. The BOE says the transfer is not handled through escrow, and a late claim gets relief only from the year it is filed.

What have Casta del Sol and Palmia homes sold for in the last 12 months?

CRMLS closed sales from Oct 19, 2025 to Oct 18, 2026 show a $895,500 median for Casta del Sol (116 sales) and $1,025,000 for Palmia (47 sales), all home types. The Mission Viejo citywide median for the same window was $1,215,000. A median is not a price for a specific home.

Downsizing? Start with what your current home would sell for.

What's your home worth today? Get a free home valuation: https://shepherdrealestateteam.com/home-valuation, or call or text Darren at (949) 806-6834.

About Darren Shepherd

Darren Shepherd leads The Darren Shepherd Team at Compass California, Inc., based in Dana Point and focused on Mission Viejo and nearby South Orange County cities. Mission Viejo is Darren's main market. With over a decade in real estate, he has 200+ homes sold and $210M+ in sales, including 41 homes closed in 2025. His specialties are Military/Veterans and Senior Communities. Darren is a RamseyTrusted agent. Call or text (949) 806-6834.

Darren Shepherd is a California real estate salesperson, CA DRE #02000042. Responsible broker: Compass California, Inc., CA DRE #01991628.

Darren Shepherd, real estate salesperson, CA DRE #02000042 | Office: Compass, 33522 Niguel Road, Suite 100, Dana Point, CA 92629 | Responsible broker: Compass California, Inc., DRE #01991628