Last updated September 2026. The value limit referenced below adjusts every two years; the next adjustment is February 2027.

Most people who have owned a home in Sonoma County for decades believe the same thing: that selling it and buying another would reset their property taxes to today's value. For a homeowner assessed at $180,000 in a house now worth $1.1 million, that belief is worth thousands of dollars a year — and it keeps people in houses that no longer fit.

Since April 1, 2021, it has not been true. Proposition 19 lets California homeowners who are 55 or older take their Proposition 13 assessed value with them when they move.

What Proposition 19 actually changed

Proposition 19 passed in November 2020 and did two very different things. They are constantly confused with each other.

The half that gets the attention is about inheritance. It narrowed what parents can pass to children without reassessment, and it took effect February 16, 2021. That half is genuinely restrictive, and I have written about it separately on the inherited property page.

The other half took effect April 1, 2021 and went the opposite direction. It expanded a benefit that had existed since the 1980s under Propositions 60 and 90, and removed the restrictions that made the older benefit nearly unusable.

Under the old rules, a homeowner 55 or older could move their assessed value once, to a home of equal or lesser value, and only within their own county — or into one of ten counties that had adopted an ordinance accepting transfers from elsewhere. Sonoma County was not one of those ten. For a Sonoma County homeowner, leaving the county meant leaving the Proposition 13 tax base behind.

	Old rules (Prop 60/90)	Now (Prop 19)
Where	Same county, or 10 participating counties	Any of California's 58 counties
Price	Equal or lesser value only	Any value; excess above a threshold is added
How many times	Once, ever	Up to three times

Who qualifies

Four conditions, all of which must be met.

1. Age

You must be at least 55 at the time you sell the original home. If you are married and living together, only one spouse needs to meet the age requirement. You may be under 55 when you buy the replacement — the age test is measured at the sale. Homeowners who are severely and permanently disabled, and victims of a wildfire or Governor-proclaimed natural disaster, qualify regardless of age under their own tracks and forms.

2. Both homes must be primary residences

The home you sell must have been your principal residence, and the home you buy must become your principal residence. A vacation home does not qualify on either end. Neither does a rental or investment property.

3. Two years

The sale of the original home and the purchase or new construction of the replacement must fall within two years of each other. The order does not matter — you may buy first and then sell, or sell first and then buy. Miss the window and the replacement home is assessed at full market value, with no partial credit.

4. You have to file

The transfer is not automatic. You file Form BOE-19-B with the assessor in the county where the replacement home is located, within three years of purchasing or completing it. Filing late can limit relief to future years rather than back to the date you moved in. In my experience this is where most of the damage gets done — the transaction closes, everyone moves on, and the claim never gets filed.

The value test: what happens if the new home costs more

If the replacement home is worth the same as or less than the home you sold, your assessed value transfers intact and nothing is added.

If the replacement is worth more, the amount above a threshold is added to your transferred value. The threshold depends on when you buy relative to when you sell:

• 100% of the original home's market value, if you buy before you sell
• 105%, if you buy within the first year after the sale
• 110%, if you buy within the second year after the sale

This surprises people: buying before you sell gives you the least generous threshold. Selling first and buying within twelve months gives you a five percent cushion. That is a real trade-off against the convenience of buying first, and it is worth thinking through before you write an offer rather than after.

A worked example

You sell a Santa Rosa home for $1,100,000. Your factored base year value is $180,000, because you bought in the 1990s. Nine months later you buy a replacement home for $1,300,000.

Because you bought within the first year after selling, your threshold is 105% of $1,100,000, or $1,155,000. The excess is $145,000. That amount is added to your transferred base, so your new assessed value is $325,000 — not $1,300,000.

Your property tax bill does go up. But you bought a $1.3 million house and you are taxed as though it were worth $325,000.

These figures are illustrative. Market value is determined by the county assessor, not by the purchase price alone.

Three transfers, and why that matters

Under the old law you had one transfer, ever. That single fact kept people in houses that had stopped working for them, because they were afraid of spending their one chance on the wrong home.

Proposition 19 allows up to three. You can downsize now and adjust later if the location does not work or your circumstances change. And if you already used a transfer under Proposition 60 or 90 before April 2021, you still get three under Proposition 19.

If you rebuilt after a wildfire

Sonoma County has thousands of households in a specific situation: they rebuilt after Tubbs, Nuns, Kincade or Glass, and kept most of their original tax base, because a reconstruction that is substantially equivalent to what was destroyed is not treated as new construction. Many of those owners assume that tax base is permanently tied to that address.

It is not. If you are 55 or older, the same base year value transfer is available to you. One caveat: if the rebuild came back larger or better than what burned, some of the difference may have been added to your assessment as new construction — so your base may not be exactly what it was before the fire. Worth establishing the real number before making any decisions.

What this does not do

• It does not cover second homes or rental property. Both properties must be primary residences. Income property is a separate analysis with a very different answer.
• It does not help your children. What happens when property passes to the next generation is governed by the other half of Proposition 19, and those rules are considerably tighter — particularly for anything that was not the parent's primary residence.
• It is not automatic. No form, no benefit.
• It is not tax or legal advice. I am a real estate broker. What I can tell you is what this means for the timing, sequencing and structure of a move. How it interacts with your estate plan, your capital gains position or your trust is a question for your CPA and your attorney, and the good ones want to be in the conversation early.

Common questions

Can I transfer my property tax base out of Sonoma County?

Yes. Since April 1, 2021, a base year value transfer may be made to a replacement primary residence in any of California's 58 counties. Under the old Proposition 60 and 90 rules this was not possible from Sonoma County, because Sonoma had not adopted an ordinance accepting intercounty transfers.

Does my new house have to cost less than the one I sold?

No. Under Proposition 19 the replacement home may be of any value. If it costs more than the threshold that applies to your timing — 100%, 105% or 110% of the original home's market value — the excess is added to your transferred base year value, rather than the whole property being reassessed.

How many times can I transfer my Proposition 13 base year value?

Up to three times, for homeowners 55 and older or severely and permanently disabled. Transfers used under the old Proposition 60 or 90 rules before April 2021 do not count against the three.

How long do I have between selling and buying?

Two years. The purchase or new construction of the replacement primary residence must occur within two years of the sale of the original, in either order.

What form do I file, and where?

Form BOE-19-B, filed with the assessor in the county where the replacement home is located, within three years of the purchase or completion of construction.

Do both my old and new home have to be my primary residence?

Yes. The home you sell must have been your principal residence and the replacement must become your principal residence. Vacation homes and rental properties do not qualify on either end.

I rebuilt my home after a wildfire. Can I still transfer my base year value?

Generally yes, if you meet the age and residence requirements. A rebuild that was substantially equivalent to the destroyed home retains the original base year value, and that value can then be transferred. If the rebuild was larger or better than what was destroyed, part of the difference may have been assessed as new construction.

Related: What Proposition 19 means for inherited property in California — the other half of the law, covering what happens when property passes from parents to children.

This page is general information about California property tax law and is not tax or legal advice. Property tax outcomes depend on facts specific to your property and are determined by the county assessor. Consult your CPA or attorney regarding your situation. Daniel Rogers, Broker Associate, Century 21 Epic Valley of the Moon, DRE #02051470.