Why Your Pleasanton Property Tax Basis Couldn't Always Follow You to Vineyards at Marsh Creek

If a neighbor tells you they moved across the Bay Area years ago and kept their old property tax bill, ask which two counties were involved before you assume the same trick works for you. For one specific and increasingly common move among Tri-Valley homeowners, from a long-held house in Pleasanton (Alameda County) to a resale home at Vineyards at Marsh Creek in Brentwood (Contra Costa County), the honest answer for most of the past three decades was that it couldn't be done. Not because the homeowner was too young, not because the new home cost too much, but because of where the new home happened to sit.

That changed on April 1, 2021. If you're 55 or older and thinking about trading a Pleasanton house for a single-story resale home in the gated community known as Trilogy at The Vineyards, the rule that used to block this exact route is gone. Most homeowners who've heard about property tax portability picture it as something that's always existed in some form. For this particular county pairing, it hasn't.

The Rule Depended on Where You Were Going, Not Where You'd Been

California has let homeowners 55 and older carry a low property tax basis to a new home since 1986, but the original version, Proposition 60, only worked within the same county. Two years later, Proposition 90 opened the door to moves across county lines, with one condition: the county you were moving into had to have passed its own ordinance agreeing to accept incoming transfers. Alameda County, where Pleasanton sits, was one of the counties that opted in, and stayed opted in for decades. That fact turns out to be irrelevant to this specific move, because Prop 90 eligibility was governed by the destination county's rules, not the origin county's.

Contra Costa County, where Brentwood and Vineyards at Marsh Creek sit, repealed its own Prop 90 ordinance in the early 1990s. A 2007 push by the county assessor to bring it back for a two-year trial run, aimed at reviving a sluggish housing market, never gained traction with the Board of Supervisors. So for the entire stretch when Trilogy at The Vineyards was being built out and sold, a Pleasanton homeowner selling a long-held house and buying there could not bring their old tax basis with them. Alameda's willingness to let transfers in didn't matter, because the transfer would have needed to land in a county that had already said no.

The rule people remember from the 1990s and 2000s wasn't a general California policy. It was a patchwork of individual county decisions, and Contra Costa had opted out of the part that would have mattered for this move.

What Changed on April 1, 2021

Proposition 19, passed by voters in November 2020, replaced the whole county-by-county opt-in system. Under the version of the law in effect today, and confirmed unchanged for 2026, a homeowner 55 or older can transfer their factored base year value to a replacement home in any of California's 58 counties, no local ordinance required. The lifetime limit went from one transfer under the old rules to three. And the replacement home no longer has to be of equal or lesser value: you can buy up, though any amount above your original home's value, adjusted by 100, 105, or 110 percent depending on timing, gets added to the transferred base year value rather than wiping it out.

Here's the before-and-after for this specific route:

What the Math Looks Like Today

Say a Pleasanton homeowner bought their house decades ago for a fraction of today's prices. Under Proposition 13, assessed value can only climb 2 percent a year, so a home bought for well under $500,000 in the late 1990s could easily carry a factored base year value in the $650,000 to $750,000 range today, even as the market value climbed far higher. Pleasanton's single-family median sale price sat around $1.5 million as of the three months ending May 2026, with homes typically moving in about three weeks. Sell at that level and the old base year value, not the sale price, becomes the number you're allowed to carry forward.

A resale home at Vineyards at Marsh Creek priced at or below the applicable percentage of that sale price (100 percent if you buy before you sell, 105 percent within the first year after, 110 percent within the second year) lets the entire old base year value transfer intact. Buy above that threshold and only the excess gets added to your new taxable value. Either way, the gap between a factored base year value in the $700,000 range and a replacement home purchased near $1 million or more is not small. California taxes assessed value at just over 1 percent, plus local voter-approved add-ons, so a few hundred thousand dollars of avoided reassessment is a real, recurring number on every future tax bill, not a one-time discount.

Filing Lands in Martinez, Not Pleasanton

One detail trips people up: you file the claim with the assessor's office in the county where the replacement property sits, not where you sold. For a move into Vineyards at Marsh Creek, that means the Contra Costa County Assessor's Office in Martinez, not Alameda County. You have two years from the sale of your Pleasanton home to complete the purchase in either order, and three years from the purchase date to file the claim for full retroactive relief. File later and the tax relief starts the year you actually file, not the year you moved in.

Both properties also have to qualify for the homeowners' exemption, meaning both need to have been your principal residence, not a second home or rental, either at the time of sale or within the two-year window. If you buy the Brentwood home before your Pleasanton house sells, you'll pay full assessed taxes on the new home in the meantime. The transferred base year value only kicks in once the original sale closes.

Before you call the assessor's office, it helps to have on hand:

• The sale date and sale price of your Pleasanton home, or your best estimate if it hasn't sold yet
• Your most recent property tax bill showing the current factored base year value
• The purchase price and closing date (actual or anticipated) for the Vineyards at Marsh Creek home
• Confirmation of who will be on title for the replacement property

Why Timing Matters More at Vineyards at Marsh Creek Specifically

Trilogy at The Vineyards is a resale-only market now that Shea Homes has closed out new construction, with roughly 1,100 homes across the community and resale square footage typically running from about 1,465 to nearly 2,900 square feet. Because inventory turns over one household at a time rather than through a builder's release schedule, the right floor plan at the right price doesn't always appear on your preferred timeline. That makes the two-year Prop 19 window worth planning around early rather than treating it as a formality. If you want more detail on what the resale process there actually looks like, our guide to buying in Vineyards at Marsh Creek and our look at daily life inside the community cover HOA structure, amenities, and what to check before removing contingencies.

A Few Questions We Hear Often

Does my age when I buy the Brentwood home matter? No. You only need to be 55 or older on the date you sell your original Pleasanton home. If you were 54 at closing, you don't qualify, regardless of your age when you complete the purchase later.

What if I want to buy at Vineyards at Marsh Creek before my Pleasanton home sells? You can, and the two-year window runs the same either way. You'll simply pay taxes on the new home's full assessed value until your original home closes, at which point the base year value transfer takes effect.

Can my adult child be added to the title without disqualifying me? No. As long as you were an owner and occupant of the original Pleasanton home and you're one of the purchasers of the new one, a co-owner on title, including an adult child helping with the purchase, doesn't affect your eligibility. The full transferred value applies to the entire replacement property.

None of this replaces advice from your own tax professional or the assessor's office directly, but understanding which rule actually governs your specific move, rather than the general idea of "Prop 13 portability," changes how you plan the sale, the search, and the timeline in between.

If you're weighing a move from Pleasanton to Vineyards at Marsh Creek, or just trying to understand what your current home's tax basis is actually worth in a decision like this one, Jo Ann Luisi has spent years helping Tri-Valley homeowners work through exactly this kind of transition, from the numbers to the timeline to the moving truck. If parents or a family member are part of this conversation, our step-by-step guide to helping parents sell a Pleasanton home is a good place to start. Request your free home valuation and consultation whenever you're ready to see what the math looks like with your actual numbers.