Prop 19 Portability Between California Counties Explained

Editorial note: Gold California is not a tax advisor, a licensed attorney, or a county assessor. This page is a plain-English explainer of California Proposition 19 base year value portability between counties. It serves homeowners age 55 and older, severely disabled homeowners, wildfire and disaster victims, surviving spouses, and adult children.

Every figure, date, form number, and code section is cited to the California Board of Equalization or to the California Revenue and Taxation Code. Consult a licensed California CPA, attorney, or your county assessor for your specific situation.

Last updated: August 15, 2026 · By Gold California Editorial

This page explains how the base year value portability rule under Proposition 19 works when a California homeowner moves between counties. It covers what changed on April 1, 2021, what every county assessor is now required to do, which BOE form is filed and where, and the practical steps a claimant takes on a cross-county move.

Every date, form number, and code section is cited to the California Board of Equalization or to Revenue and Taxation Code section 69.6. This is not tax advice; consult a licensed California CPA, attorney, or your county assessor before relying on any of it for your situation.

What Prop 19 portability between counties means

Portability, in California property tax language, means the taxable value that a homeowner has built up on an original primary residence under Proposition 13 can be transferred to a new primary residence. The transferred number is called the factored base year value. It is usually far lower than the current fair market value of the home.

Under Proposition 19, that transfer is available to a qualifying homeowner even when the two homes are in different California counties. The claimant does not have to stay in the same county to keep the low base. The California Board of Equalization confirms that the transfer is statewide, from any county to any county (source: BOE, Proposition 19 FAQs).

The rule is written in Revenue and Taxation Code section 69.6 and is implemented by the BOE through Letters to Assessors. It applies to three qualifying categories: homeowners age 55 or older, severely and permanently disabled homeowners, and victims of a Governor-proclaimed wildfire or natural disaster.

The pre-2021 patchwork under Propositions 60 and 90

Before Proposition 19, the base year value transfer rule for age 55 or older claimants lived in Revenue and Taxation Code section 69.5 and was created by Propositions 60 (1986) and 90 (1988). Proposition 60 covered intracounty transfers, meaning inside the same county. Proposition 90 opened the door to intercounty transfers, but only if the county of the replacement had enacted a local ordinance accepting them.

That ordinance requirement created a patchwork. Most California counties chose not to enact a Proposition 90 ordinance, so a senior selling in a Prop 90 county and buying in a non-participating county could not carry the base year value across. In practice, only a small group of counties accepted intercounty transfers, and the list changed over time. The BOE explains the prior system in its Letter to Assessors No. 2021/019 (source: BOE Letter to Assessors No. 2021/019).

Under the prior rule, a homeowner in Los Angeles County could sell and buy in Los Angeles County without any county-line question. A homeowner in Los Angeles County selling and moving to a county that had not enacted a Prop 90 ordinance lost the low base entirely. The unfairness of that county-by-county opt-in was one of the reasons voters were asked to consider Proposition 19 in November 2020.

The statewide rule since April 1, 2021

Proposition 19 replaced that patchwork. The new rule lives in section 2.1(b) of article XIII A of the California Constitution and is implemented by Revenue and Taxation Code section 69.6. Together they allow an eligible homeowner to transfer the taxable value of a primary residence to a replacement primary residence anywhere in California, on and after April 1, 2021 (source: BOE Letter to Assessors No. 2021/019, page 1).

The BOE addresses the county-ordinance question directly. In its Q13 answer, the Letter states that there is no requirement that a county enact an ordinance in order to allow an intercounty base year value transfer under Proposition 19 (source: LTA 2021/019, Question 13). Every one of the 58 California county assessors must accept a qualifying claim.

The rule cap for age 55 or older and severely disabled claimants is three base year value transfers over a lifetime. The BOE clarifies that this cap resets regardless of whether the claimant previously used the one-time transfer under Propositions 60, 90, or 110. A claimant who used the old one-time transfer can still transfer three more times under Proposition 19 (source: LTA 2021/019, Question 15).

Wildfire and Governor-proclaimed disaster victims are treated separately in section 69.6 and are not subject to the three-use cap in the same way. Their claim runs on Form BOE-19-V and requires proof that the original home was substantially damaged, which the statute defines as damage to more than 50 percent of the improvement value (source: BOE Letter to Assessors No. 2022/009).

Which county assessor takes the claim?

The claim is always filed with the county assessor of the replacement primary residence. That is the assessor who will apply the transferred factored base year value to the new property. It does not matter which county the original home is in; the replacement county assessor is the one who administers the claim.

The replacement county assessor coordinates with the original county assessor to confirm the factored base year value that transfers. In practice, the replacement assessor pulls the original property's roll data by parcel number, verifies the sale price and closing date, and applies the value comparison test in section 69.6.

The correct claim form for an age 55 or older claimant is BOE-19-B, titled "Claim for Transfer of Base Year Value to Replacement Primary Residence for Persons at Least Age 55 Years." Every California county assessor publishes BOE-19-B, BOE-19-D, and BOE-19-V on its website. The forms are identical statewide, but the mailing address, drop-off counter, and any local supplemental sheets vary by county (source: BOE, Proposition 19 Forms page).

How the value comparison works in a cross-county move

Whether the base year value transfers in full or with an upward adjustment depends on a value comparison between the two homes. The comparison uses full cash value, which the statute defines as fair market value at the time of sale or purchase.

If the replacement's full cash value is equal to or less than the original's, the replacement is taxed on the transferred factored base year value. That is the plain transfer case. If the replacement is more expensive, the transferred base is increased by the difference between the two full cash values. Section 69.6(b)(3) sets the formula, and BOE Letter to Assessors No. 2022/009 explains it (source: LTA 2022/009, pages 11 to 12).

The value comparison uses one of three timing factors on the original's full cash value, depending on when the replacement is bought or built.

• 100 percent of the full cash value of the original, if the replacement is purchased or newly constructed before the sale of the original.
• 105 percent of the full cash value of the original, if the replacement is purchased or newly constructed within the first year after the sale.
• 110 percent of the full cash value of the original, if the replacement is purchased or newly constructed within the second year after the sale.

The timing factor never rounds. It is exactly 100, 105, or 110 percent applied to the original's full cash value. This is not the same as the parent-child $1,000,000 upward adjustment threshold under section 63.2, which is a different Proposition 19 rule and covers different property (source: BOE Letter to Assessors No. 2020/061).

How to file a Prop 19 cross-county base transfer, step by step

The steps below are for the most common case: an age 55 or older claimant selling an original primary residence in one California county and buying a replacement primary residence in another California county. The path for BOE-19-D and BOE-19-V is nearly identical, with the added attachments each form requires.

1. Confirm the qualifying category and date. Age 55 or older on the date of sale of the original primary residence, severely and permanently disabled, or a victim of a Governor-proclaimed disaster. Pick the matching claim form: BOE-19-B, BOE-19-D, or BOE-19-V.
2. Confirm at least one transaction is on or after April 1, 2021. If both the sale and the purchase closed before April 1, 2021, the transfer is governed by the older section 69.5 rules (Propositions 60, 90, and 110), not Proposition 19.
3. Line up the two full cash values. Sale price on the original from the closing statement, and purchase price or completed-construction full cash value on the replacement.
4. Confirm the two-year window is intact. The sale and the purchase or new construction must fall within a two-year window of each other, in either order.
5. Download BOE-19-B from the county assessor of the replacement home. Every California county publishes the current BOE-19-B on its website. The form is identical statewide.
6. Complete the form. Fill in claimant information, both properties, the qualifying category, the date of birth or disability certification, and the requested attachments (settlement statement, recorded deed, and identification).
7. File within three years of the replacement's purchase or completion. Filing on time secures a retroactive base year value transfer to the acquisition date of the replacement.
8. File the homeowners' exemption on the replacement within one year. Form BOE-266, filed with the same replacement county assessor. It provides the $7,000 principal-residence assessment reduction and confirms residency for section 69.6.
9. Keep copies of the claim, deed, and tax bill. Retain records for at least four years after the transfer is granted, in case the assessor follows up.

Key California county assessor Prop 19 pages and phone numbers

The table below lists the assessor landing pages and main phone numbers for the ten most populous California counties. Every county assessor is required to accept a qualifying Proposition 19 claim; these are the practical starting points for downloading the claim form and reaching the office.

Sources: California State Board of Equalization, County Assessor Directory (contact information) and each county assessor's official website. Checked August 2026. Phone numbers rotate; call to confirm the current Prop 19 desk before mailing anything.

A worked example, Los Angeles to Sacramento

The worked example below uses the standard section 69.6 rule for an age 55 or older claimant moving from Los Angeles County to Sacramento County. Numbers are illustrative and the sequencing follows the statute.

County-level differences that still exist under Prop 19

Section 69.6 is a statewide law, and every California county assessor administers it. That said, a few practical details do vary by county, and those variations matter for a cross-county filer.

• Supplemental sheets. Some large-county assessors (for example Los Angeles, San Francisco, and Santa Clara) attach a local claim-status tracking sheet or a supplemental disclosure to the BOE form. It is not a separate legal step; it is a county intake convenience.
• Online submission. Several counties accept an uploaded PDF or an online portal submission. Others still require paper filing by mail or in person. Los Angeles County posts current filing instructions on its Proposition 19 page.
• Recording versus filing. The claim itself is a confidential document filed with the assessor, not recorded with the county recorder. The documents that are recorded, and that the assessor pulls, are the deeds on the original sale and the replacement purchase.
• Coordination time. A cross-county claim usually takes longer than a same-county claim, because the replacement assessor has to pull data from the original county assessor. Six months to nine months is not unusual for a straightforward case.
• Local property tax rates. The transferred factored base year value is the same across counties, but the effective property tax rate is not. Each county's mix of voter-approved bonds and Mello-Roos districts changes the annual bill on the same assessed value. This is a separate calculation from the section 69.6 transfer.
• Homeowners' exemption filing address. BOE-266 is filed with the county assessor of the replacement home. If the mailing address on file is still the original county, the exemption notice can be missed. Update the address early.

If a county's website posts a different filing address or an added attachment list, follow that county's instructions. The core BOE form, the statutory deadlines, and the value comparison test do not change between counties (source: BOE, Proposition 19 FAQs).

When a cross-county Prop 19 transfer is a bad idea

A balanced page names when the portability rule argues for slowing down rather than filing. Section 69.6 caps age 55 or older claimants at three transfers over a lifetime. A wasted filing is a wasted slot.

• The original home was never a principal residence. Rentals, second homes, and vacation properties do not qualify. Filing anyway wastes assessor time and starts a paper trail you may have to correct.
• The two-year window is already closed. A sale-to-purchase gap greater than two years cannot be reset. Filing to test the assessor is a wasted claim.
• The replacement is far more expensive than the original. Every dollar the replacement exceeds the adjusted original is added to the transferred factored base year value, so most of the property tax saving evaporates. Consider whether the slot is worth using.
• Another move is likely within a few years. Each move uses one of three slots. If a downsizing move is likely to be followed by another (for care, family, or a smaller home), keeping at least one slot in reserve is often the right call.
• You are planning to leave California. The transfer is statewide inside California only. A move to Nevada, Arizona, Texas, or any other state does not carry a California factored base year value with it. See the staying versus leaving California comparison for the broader tax picture.
• You are relying on the parent-child rule instead. Section 63.2 is a different Proposition 19 rule (parent-child transfer of the family home) and is not the base year value transfer for age 55 or older claimants. The two rules use different forms and different value tests.

If any of these describes your situation, wait, get advice from a licensed California CPA or attorney, and revisit the timing later. The portability rule rewards planning; it does not reward rushing.

Prop 19 county portability questions, answered

Can I transfer my base year value to any California county under Prop 19?

Yes. Since April 1, 2021, Proposition 19 allows a qualifying homeowner to transfer the factored base year value of an original primary residence to a replacement primary residence located anywhere in California, regardless of the location or value of the replacement. Every one of the 58 California county assessors must accept a qualifying claim (source: BOE Letter to Assessors No. 2021/019).

Does the county of my replacement home have to have opted in?

No. The California Board of Equalization has confirmed in Question 13 of Letter to Assessors No. 2021/019 that there is no requirement that a county enact an ordinance in order to allow an intercounty base year value transfer under Proposition 19. The prior county-by-county opt-in rules under Propositions 60 and 90 no longer apply to sales on or after April 1, 2021.

Which county assessor do I file the claim with?

You file with the county assessor of the replacement primary residence. That assessor administers the claim, applies the value comparison test, and coordinates with the original county assessor to confirm the factored base year value that transfers. The claim is not filed with the original county assessor.

What form do I use for a cross-county Prop 19 base transfer?

Form BOE-19-B if you are age 55 or older on the date of sale of the original home. Form BOE-19-D if you are severely and permanently disabled. Form BOE-19-V if the original home was substantially damaged or destroyed by a wildfire or Governor-proclaimed disaster. Every California county publishes the current forms on its assessor website.

How many times can I use the Prop 19 transfer?

Age 55 or older and severely disabled claimants are capped at three transfers over a lifetime under Revenue and Taxation Code section 69.6. The BOE has clarified that use of the older one-time transfer under Propositions 60, 90, or 110 does not count against the three-use cap. A claimant who previously used the old transfer can still use three transfers under Proposition 19.

Does moving to a more expensive home in a different county still work?

Yes, but the transferred taxable value is adjusted upward. The formula is (replacement full cash value minus original full cash value adjusted by the applicable 100, 105, or 110 percent timing factor) added to the original's factored base year value. The transfer still happens; the tax saving is smaller than a straight equal-or-lesser-value transfer.

If I sold my Los Angeles home before April 1, 2021, do I still qualify for a statewide transfer?

Not under Proposition 19. If both the sale of the original and the purchase of the replacement closed before April 1, 2021, the transfer is governed by the older section 69.5 rules (Propositions 60, 90, and 110). The intercounty transfer under the older rules is only available if the county of the replacement had enacted an opt-in ordinance. If at least one of the two transactions is on or after April 1, 2021, Proposition 19 rules apply.

Does the Prop 19 base transfer help with my California income tax or federal capital gains?

No. Proposition 19 changes the local property tax base year value on the replacement home. It has no effect on California state income tax, on federal income tax, on the Internal Revenue Code section 121 capital-gains exclusion on the home sale itself, or on any retirement account rule. Those are separate tax systems; consult your tax advisor for your specific situation.