The short answer: If your unpermitted ADU or JADU was built before January 1, 2020 without a permit, California law (Government Code section 66311.7, expanded by AB 2533) lets you apply to legalize it. The city cannot deny the permit because the unit violated the building code in effect when it was built, and cannot deny it for not meeting current ADU standards. It can deny it if the unit fails basic health and safety standards from Health and Safety Code section 17920.3. Legalization is therefore a safety question, not a zoning question.
Last verified: October 5, 2026 ยท Written by the ADU Scope editorial team
Attention: This article is general information for owners of existing units. If your unit was built in 2020 or later, or was never habitable, the amnesty does not apply, and you should speak with a local attorney or permit expediter before contacting the city.
Who Qualifies to Legalize an Unpermitted ADU
The ABAG/MTC guidance memo on the law says ADUs and JADUs “originally built prior to January 1, 2020” are eligible under Government Code section 66311.7. Orange County’s program adds that the unit must meet the state’s ADU definitions and involve new square footage or the conversion of an existing structure, such as a garage.
The cut-off date matters because it marks the moment when California began broadly legalizing ADUs. Units built after that date were already covered by the standard permitting rules, so there was less reason for amnesty.
Typical situations
- Garage converted into a studio without permits before 2020.
- Basement apartment created by a previous owner.
- Backyard cottage or shed converted into living space.
- Room addition with a kitchen and separate entrance.
The unit must be evidenced as pre-2020. Cities may ask for proof such as utility bills, tax records, aerial images or affidavits, but state law does not require a specific document, according to the guidance memo. Gather several kinds of evidence early.
What the City Can and Cannot Do
The guidance memo describes clear duties for cities and clear limits on them.
| Cities must | Cities cannot |
|---|---|
| Provide a legalization process for unpermitted units | Deny a permit because the unit violated the building code in effect when it was built |
| Publish a checklist of health and safety standards from Health and Safety Code section 17920.3 | Deny a permit for noncompliance with local or state ADU laws |
| Allow confidential third-party inspections before you apply | Charge “penalty fees” or connection or impact fees, with limited exceptions for utility infrastructure |
| Post the requirements on websites and permit materials | Require standards beyond those in section 17920.3 |
The fee limit is important. Normally an owner who builds without a permit faces penalty fees or doubled permit fees. For amnesty projects, the memo says cities cannot charge penalty fees or connection and impact fees, other than limited utility-infrastructure exceptions. Ordinary permit, plan-check and inspection fees are different, and no published total is available.
Tip: Use the confidential third-party inspection. It lets you learn what is wrong before the city sees it, so you can budget repairs and decide whether legalization is worth it.
The Health and Safety Standard
This is where legalization succeeds or fails. The city must limit its requirements to those in Health and Safety Code section 17920.3, which defines substandard housing. Units that fail these standards can be denied legalization, and the guidance memo says so directly.
What a safety review typically looks at
- Safe, working electrical, plumbing and heating systems.
- Adequate sanitation, including a bathroom and kitchen.
- Safe exits and structural condition.
- Working smoke and carbon monoxide alarms.
These are the general categories that housing-safety checklists cover. Your city’s published checklist, based on section 17920.3, is the authoritative list, so read it before you hire anyone. There is no single statewide checklist: cities publish their own, such as Los Angeles’s Form AB2533-01 and San Mateo County’s substandard housing checklist. The memo also flags unclear interaction between section 66311.7 and Health and Safety Code section 17980.12 on post-legalization code enforcement, so ask the city how it handles that.
Step-by-Step: How the Process Works
Orange County’s AB 2533 program gives a clear example of the sequence. Your city may differ, so use this as a model.
- Confirm eligibility. Check that the unit existed before January 1, 2020 and meets the ADU or JADU definition.
- Optional inspection. Hire a licensed contractor for a confidential third-party inspection using the housing inspection checklist. In Orange County, results are informational only and not required for the application.
- Apply for a permit. Submit an application noting that it is an AB 2533 legalization. Include proof of pre-2020 construction, site plans, property details, utility locations, parking arrangements and safety compliance details.
- Pay fees and inspect. After the permit is issued and fees paid, complete the required inspections.
- Final inspection. If the unit meets section 17920.3 standards, you receive a certificate of occupancy.
The program page mentions a “required permit deposit fee” but gives no amounts. That is typical: costs depend on the work needed. Rather than quote an unverified average, we recommend getting a written fee schedule from your city and a contractor’s estimate for any repairs.
Cost: What Drives It
No reliable official statewide cost figure is available for legalizing an unpermitted ADU. What can be said is what the cost depends on:
- Condition of the unit. Repairs to wiring, plumbing or egress are often the largest cost.
- City fees. Permit, plan-check and inspection fees vary by city, while penalty and impact fees are restricted for amnesty projects.
- Professional help. Drawings of an existing building, structural or electrical reports.
- Utilities. Any separate connection work the unit needs.
Tip: Build your budget in two parts: the city’s fees (get them in writing) and the repairs your third-party inspection identifies. Add a contingency, because old work often hides problems behind walls.
Unpermitted ADU in California: what AB 2533 changed
AB 2533 (Chapter 834, Statutes of 2024) took effect on January 1, 2025. Its main change, according to the state housing agency’s (HCD) 2025 handbook, was to move the eligibility cut-off from January 1, 2018 to January 1, 2020. The rule now sits in Government Code section 66311.7, which HCD’s March 2026 materials describe as formerly section 66332. If you read older guides, expect the old number.
The core rule, in HCD’s words, is that a local agency shall not deny a permit for a qualifying unpermitted ADU because it violates building standards, because it does not comply with state ADU law, or because it violates a local ADU ordinance. There are two exceptions: the agency can deny if it finds that correcting the violation is necessary to protect public health and safety, or if the building is substandard under Health and Safety Code section 17920.3. In a 2025 letter to Los Angeles, HCD added that when the agency finds health and safety problems, it must approve the permits needed to correct them.
Two clarifications from HCD matter for owners. The provision does not cap the number of ADUs a city must approve. And a unit created by dividing existing living space, such as splitting an apartment, is not treated as a conversion of non-livable space under section 66323(a)(3).
Deferring enforcement on an unpermitted ADU: the five-year delay
The “five years” you may have heard about comes from a different law. Health and Safety Code section 17980.12, amended by SB 1514 (Chapter 494, Statutes of 2024, effective January 1, 2025), says that until January 1, 2030 a city that sends a notice to correct a building-standards violation must tell the owner that they can request a delay of enforcement.
- It covers ADUs built before January 1, 2020, and ADUs built later in a jurisdiction whose ADU ordinance was non-compliant at the time but is compliant when the owner asks.
- The owner can request a five-year delay on the ground that correcting the violation is not necessary to protect health and safety. The city must grant it if it determines that is true, after consulting the State Fire Marshal’s office under Health and Safety Code section 13146.
- No new requests are accepted from January 1, 2030, and delays already granted run for their full term.
- A city cannot require an owner to fix a violation in the main house that is not necessary for health and safety as a condition of ministerially approving the ADU.
- The section is repealed on January 1, 2035.
Treat the delay as a separate, defensive tool. Legalization under section 66311.7 gets the unit permitted. The delay postpones enforcement of a violation notice. Some counties describe the delay as not applying to hazardous violations, which matches the health-and-safety test in the statute.
Proving your unpermitted ADU predates 2020
State law does not name a specific document, so cities have written their own lists. Programs we reviewed (San Diego Information Bulletin 242, Hayward and Santa Clara County) accept a mix of evidence. The most common items are county assessor records, escrow and closing documents, earlier permits, insurance records, utility accounts, code-enforcement records, dated photographs, contractor invoices, leases and notarized statements from people who know when the unit was built.
Beyond proof of age, local programs ask for a site plan and floor plan, a signed habitability checklist, and sometimes affidavits for smoke and carbon monoxide alarms and water-saving fixtures (Ventura and Los Angeles County examples). These are local requirements, not state mandates. San Diego asks for more documentation in specific situations, such as fault, landslide or liquefaction zones, excavation under the floor, easements and the coastal zone, which reflects that city’s own policy.
What we could not confirm about legalizing an unpermitted ADU
- Property taxes. We found no assessor or Board of Equalization source on how a legalized unit is treated for reassessment. It depends on the county assessor, so ask before you apply.
- Financing and insurance. We found no official source. Talk to your lender and insurer before and after legalization.
- Demolition. We found no statutory text that limits a city from requiring demolition of a substandard unit. The protection in section 66311.7 does not apply to a substandard building under section 17920.3.
- Energy and green-building codes. One city says legalized units are exempt from the Energy Code and CALGreen; we could not confirm that in the statute, so ask your building department.
- Penalty wording. County and city pages say penalty fees cannot be charged, but we did not read the exact statutory sentence. See the fee limits discussed above and confirm with your city.
Frequently Asked Questions
Can the city deny my unit because it does not meet current ADU standards?
No, under the amnesty a city cannot deny a permit for noncompliance with local or state ADU laws, but it can deny a unit that fails basic health and safety standards.
Will I pay penalty fees?
The guidance memo says cities cannot charge penalty fees or connection and impact fees, with limited exceptions for utility infrastructure.
What if my unit was built in 2021?
It is outside the pre-2020 amnesty, so ordinary permit rules apply. Talk to a local professional.
Do I need an inspection before applying?
Not required, but a confidential third-party inspection is allowed and recommended.
Next Steps
- California ADU Laws 2026
- ADU Impact Fees: When You Pay Them and How to Avoid Them
- Garage Conversion to ADU: Cost, Permits and Timeline
- ADU Permit Cost by City: California Fees Compared
- Do ADUs Need Separate Utility Meters? California Rules and Practical Options
General information, not legal advice. Local rules vary and change; confirm with your planning department and a licensed attorney.
Sources: MTC/ABAG: Amnesty for Unpermitted ADUs, guidance memo (March 2026) ยท County of Orange: AB 2533 Safe ADU/JADU Legalization Program ยท HCD ADU Handbook, March 2026 ยท Health & Safety Code 17980.12 ยท HCD letter to Los Angeles (Aug. 14, 2025) ยท San Diego IB 242