Marin County Assessor-Recorder Shelly Scott certified this year's countywide assessment roll at $114.1 billion in July, an increase of 3.62 percent over last year, and described the result as "a stable Marin County real estate market." That word, stable, is accurate at the county level and almost beside the point for a longtime homeowner deciding whether to sell the house that raised their kids and move into something smaller. The number that actually matters to that household isn't the countywide roll. It's the gap between what they're assessed for today and what a replacement home will cost them in property tax the day escrow closes.
Most people assume that gap closes the moment they sell. Decades of California's Proposition 13 cap mean a home bought in the 1980s or 1990s often carries an assessed value a fraction of its current market price. The fear, reasonable on its face, is that selling erases that protection and resets the tax bill to whatever the new home is worth. For homeowners 55 or older, that fear is largely wrong, and the part most explainers skip is the detail that actually changes the math: California doesn't just let you carry your old tax base to a new home under Proposition 19. It rewards you for waiting to buy it.
What The County Roll Doesn't Tell You
The 2026 roll growth reflects new construction, ordinary Proposition 13 inflation adjustments, and properties that changed hands and got reassessed at sale. It also reflects more than $3.77 billion in assessed value that was exempted this year, mostly through the standard $7,000 homeowners' exemption available to anyone who owns and occupies their home. None of that tells an individual seller what happens to their own bill.
That answer lives in a separate, much older piece of the tax code that Proposition 19 rewrote in 2021. Before that change, a homeowner who wanted to move without a tax hit had to buy a home of equal or lesser value, and usually had to stay inside the same county or one of a short list of counties that had opted into reciprocity. Marin residents who wanted to move to, say, a coastal county that hadn't opted in were out of luck. Proposition 19 opened that up statewide and, more significantly for anyone actually shopping in Marin's current price range, stopped requiring the replacement home to cost the same or less.
The Number Most People Miss: The Adjusted Sale Price
Here's the mechanism. If you're 55 or older, severely disabled, or a wildfire or natural disaster victim, you can transfer your old factored base year value to a new primary residence anywhere in California, up to three times in your lifetime, unlimited for disaster victims. If the replacement home costs the same or less than what you sold your old one for, your assessed value doesn't change at all. If it costs more, the assessor adds the difference between the replacement's market value and an adjusted version of your original sale price, not the raw sale price itself.
That adjustment is where the timing incentive hides. The comparison figure isn't simply what you sold your house for. It's 105 percent of that price if you close on the replacement within one year of the sale, and 110 percent if you close within the second year. In plain terms, waiting longer to buy doesn't cost you the benefit. It buys you a bigger cushion before the state starts adding anything to your old tax base.
| Timing of replacement purchase | Adjusted comparison price (on a $1.6M sale) | Cushion above sale price |
|---|---|---|
| Within 1 year of selling | $1,680,000 | 5% |
| Within 2 years of selling | $1,760,000 | 10% |
A homeowner who assumes speed is the safe move, sell fast, buy fast, lock it in, is actually giving up half the available cushion. The law is built the opposite way from how most people intuit it.
Running The Math On A Marin-Sized Move
Marin County's median sale price sat at roughly $1.6 million over the three months ending in May 2026, according to Redfin's tracking, down about 5.7 percent from the same period a year earlier. Use that figure as a stand-in for a typical sale and the mechanism gets concrete.
Picture a hypothetical seller whose factored base year value, after decades of Proposition 13's 2 percent annual cap, sits at $450,000, well below the $1.6 million the home would fetch on today's market. If they close on a replacement home within the first year for anything up to $1,680,000, their assessed value on the new home stays $450,000. No blend, no increase. If they wait closer to two years and the replacement runs up to $1,760,000, the same full transfer applies.
Only once the replacement's price clears that threshold does the blend kick in. Say the same seller, closing within the second year, buys something for $1,900,000, a life plan community unit or a larger single-story replacement with $140,000 in improvements the departed house didn't have. The excess over the $1,760,000 threshold is $140,000, added to the old $450,000 base for a new assessed value of $590,000. At the roughly 1 percent base rate that Proposition 13 caps annual increases against, that's a tax bill in the neighborhood of $5,900 a year rather than the $19,000 a full reassessment on $1,900,000 would produce. Actual bills carry additional voter-approved local assessments on top of that base rate, so the real number on any specific parcel will run higher than this simplified comparison, but the shape of the gap holds.
Where This Shows Up: Life Plan Communities And The Real Cost Of Smaller
"Downsizing" in Marin doesn't always mean cheaper. Entrance fees and unit prices at local life plan communities can land close to, or above, what a seller nets from a single-family home, which is exactly when the blended formula's cushion matters most rather than least.
The Redwoods, a nonprofit senior living community that has operated on its 10-acre Mill Valley campus since 1972, houses residents ranging in age from 72 to 104 across independent living, assisted living, and skilled nursing. Villa Marin, a life plan community in San Rafael, offers condos from 660 to more than 3,000 square feet paired with a full continuum of care. One resident there described the appeal plainly: "downsizing allowed me to live more intentionally." For a couple weighing a move from a larger house into a unit at either community, the difference between a full reassessment and a blended base year value can be the line item that makes the decision.
The Filing Sequence, In Order
None of this happens automatically. The transfer requires an affirmative claim, filed correctly and on time.
- Confirm eligibility before signing anything. The base year value transfer is available to homeowners 55 or older, severely disabled homeowners, and homeowners displaced by a wildfire or other governor-declared disaster.
- Sell the original primary residence and close on the replacement within two years of each other. The order doesn't matter. You can buy the replacement before you sell, or after.
- File the Claim for Transfer of Base Year Value to Replacement Primary Residence for Persons at Least Age 55 Years with the county assessor covering the replacement home.
- If the replacement sits outside Marin, that county's assessor handles the claim, since the transfer works statewide rather than only within county lines.
- Keep both closing statements. The assessor's office verifies the claim against actual escrow paperwork, not a self-reported estimate of what either home was worth.
FAQ
Does this only work if I buy a cheaper home? No. It works if the replacement costs the same or less than your adjusted sale price, and it still provides meaningful relief above that threshold through the blended formula. Buying up in value doesn't disqualify you, it just changes how much of the increase gets added to your old base.
Can I do this more than once? Homeowners 55 or older and severely disabled homeowners can use the transfer up to three times in a lifetime. Wildfire and natural disaster victims can use it without that limit.
Do I have to stay in Marin to use it? No. The transfer applies anywhere in California. If you're leaving Marin, the claim gets filed with the assessor in whichever county the replacement home sits in, and if you're moving within Marin, it goes through the Marin County Assessor-Recorder's office.
This is general information about how the transfer works, not tax or legal advice, and the filing deadlines are unforgiving enough that a conversation with your CPA or a call to the Marin County Assessor's office before you list is worth the twenty minutes.
If you're weighing a move like this and want to talk through what your specific numbers might look like before you commit to a listing date, The Brody Team has spent four decades in Mill Valley and Marin helping owners sequence exactly this kind of transition. Contact The Brody Team.
