If you strengthen a California building against earthquakes, you can keep that work from raising your property taxes by claiming the California seismic retrofit property tax exclusion under Revenue and Taxation Code Section 74.5. You do it by filing form BOE-64 with your county assessor within 30 days of completing the project. Miss that window and the assessor is free to treat the retrofit as ordinary new construction, adding its market value to your property’s base year value and raising your tax bill.
Why the Exclusion Exists
Proposition 13 caps California property tax at 1 percent of assessed value (plus voter-approved bond rates) and limits annual increases to 2 percent.1California State Board of Equalization. California Property Tax: An Overview When you add new construction, though, the assessor values the improvement at fair market value and stacks that onto your existing base year value.2California State Board of Equalization. New Construction
Section 74.5 carves out seismic work from that treatment. If the retrofit qualifies, the assessor acts as though the improvement never happened for tax purposes, and your base year value stays put. Voters made the exclusion permanent and expanded it to cover all seismic retrofitting components on any existing building when they approved Proposition 13 of 2010.3California Secretary of State. Proposition 13 Voter Information Guide June 8, 2010 Residential and commercial owners both qualify, and the type of ownership entity does not matter.4California State Board of Equalization. Letter to Assessors No. 2010/036 – New Construction Exclusion: Seismic Retrofitting Improvements What matters is that you hold title when the work is completed. Buy a property that a prior owner already retrofitted, and you cannot claim the exclusion on that past work.
What Work Qualifies
Section 74.5 covers two overlapping categories: seismic retrofitting improvements and improvements using earthquake hazard mitigation technologies.5California Legislative Information. California Revenue and Taxation Code 74.5 In practice, that means structural strengthening intended to help a building resist earthquake forces and reduce collapse or falling hazards. Typical qualifying work includes:
- Foundation bolting that anchors a wood frame to its concrete foundation.
- Cripple wall bracing, usually plywood sheathing on the short stud walls between the foundation and the first floor.
- Shear walls that provide lateral stability.
- Parapet and appendage bracing on cornices, hanging fixtures, or exterior cladding.
- Water heater strapping to prevent gas line rupture.
The statute is not limited to that list. It points to Appendix A of the International Existing Building Code as a guide, and any work fitting the statutory definition of structural strengthening or hazard abatement qualifies.5California Legislative Information. California Revenue and Taxation Code 74.5
What Does Not Qualify
The statute explicitly excludes new plumbing, electrical work, and finishing materials tacked onto the seismic project.5California Legislative Information. California Revenue and Taxation Code 74.5 If you combine a retrofit with a kitchen remodel, the assessor shields the seismic portion and reassesses the rest. Adding square footage or converting a garage to living space also gets treated as ordinary new construction. Only costs and value directly tied to earthquake reinforcement are excluded.
This is why itemized contractor invoices matter. If your billing lumps seismic and non-seismic work together, expect the assessor to ask for a breakdown, and expect the burden to be on you to prove which dollars belong in which bucket.
How to File Form BOE-64
Claiming the exclusion means filing form BOE-64, Claim for Seismic Safety Construction Exclusion from Assessment, with the assessor in the county where the property sits.6California Department of Tax and Fee Administration. Claim for Seismic Safety Construction Exclusion from Assessment The form asks for:
- The assessor’s parcel number.
- The completion date, or anticipated completion date, of the retrofit.
- Itemized costs of the seismic components, separated from any non-seismic work.
The property owner, the primary contractor, or a licensed structural engineer or architect must also certify to the local building department which portions of the project are seismic retrofitting components under Section 74.5(b)(2).6California Department of Tax and Fee Administration. Claim for Seismic Safety Construction Exclusion from Assessment Keep every building permit issued for the project. The assessor will compare your claim against permit records.
You sign the form under penalty of perjury. Filing false information is perjury under California Penal Code Section 126, punishable by two, three, or four years in state prison.7California Legislative Information. California Penal Code 126 Prosecution over an honest mistake is unlikely, but inflating the seismic portion of a mixed project to shield remodel costs is exactly the kind of misrepresentation the certification is designed to deter.
The Two Deadlines
This is where claims most often fail. There are two separate deadlines, and missing either can cost you the exclusion.
You must notify the assessor of your intent to claim the exclusion before or within 30 days of completing the project. That notification is the BOE-64 itself. Then all supporting documents (permits, engineering certifications, contractor invoices) must reach the assessor within six months of completion.4California State Board of Equalization. Letter to Assessors No. 2010/036 – New Construction Exclusion: Seismic Retrofitting Improvements
The 30-day deadline is the one that trips people up. If you miss it, the assessor has no reason not to treat the work as ordinary new construction, and your next tax bill reflects the full market value of the improvements. Some counties may accept a late filing, but the statutory right is gone. Get the BOE-64 in before your contractor is done, not after.
What Happens After Approval
Once the assessor confirms the work fits the statutory definition and your documentation holds up, the seismic improvement value stays out of your base year value. You get official notification, and your tax bill reflects the pre-improvement valuation. There is no annual renewal. The exclusion sits on the parcel until ownership changes.
If the assessor denies the claim, you can appeal to your county’s Assessment Appeals Board. Common grounds for denial are filing past the 30-day notification deadline, failing to separate seismic costs from non-qualifying work, and lacking professional certification that the improvements meet the statutory standard. Getting a structural engineer or architect to sign off before you file, rather than after a denial, heads off most of those problems.
What Happens When You Sell
The exclusion does not transfer. When the property changes ownership, the entire property, including the previously excluded seismic improvements, is reappraised at full cash value as of the transfer date.4California State Board of Equalization. Letter to Assessors No. 2010/036 – New Construction Exclusion: Seismic Retrofitting Improvements The BOE-64 says so directly: the exclusion expires upon change in ownership.
The practical effect is that your tax savings last only as long as you own the building. A buyer paying market price for a retrofitted property will be assessed on that purchase price, which already reflects the seismic work. The exclusion is yours, not the next owner’s, and that reality should shape how you think about the payoff period on a retrofit you are considering now.