California's ADU amnesty: can your unpermitted unit be legalized?

A garage that became a bedroom and bath, a back cottage someone rented out for years, a basement with its own entrance. If a living unit like that was built without a permit, California law now gives it a much easier way to become legal, as long as it was built before January 1, 2020 and it is safe. Here is what the law says, who qualifies, and how the local cities handle it.

What the law says

Since January 1, 2025, California law says a local agency may not deny a permit for an unpermitted ADU or junior ADU built before January 1, 2020 just because it breaks the building standards or the local ADU rules. The exception is a unit that fails the state's substandard-housing standard in Health and Safety Code 17920.3, the list that covers things like structural hazards, faulty wiring, missing sanitation and fire hazards. The rule was passed as AB 2533 and was later renumbered to Government Code section 66311.7. The state housing department's ADU Handbook uses the new number. Older articles, and some city web pages, still cite the old number, Government Code 66332. It is the same law.

Who qualifies

The unit has to be an ADU or a junior ADU, a separate living space with its own kitchen and bath, or a junior unit inside the house. It has to have been built or converted before January 1, 2020. And the lot has to allow an ADU at all. A patio cover, a deck or an addition to the main house is not an ADU, so it goes through the normal legalization process instead. For that, see our guide to legalizing an unpermitted addition.

Proving the build date

The owner carries the burden. San Jose's FAQ says that if the applicant cannot provide factual records showing the unit was built before January 1, 2020, it must be permitted under current code as a new ADU. Gather what you have before you apply: dated photos, old listings, rental records, utility bills and anything else that shows the unit existed. Ask the city what it accepts before you count on a document.

What the city can still require

The law limits denial. It does not make the unit legal as it stands. Expect an inspection against the health and safety list, and plan to fix what fails, which can mean electrical, smoke and carbon monoxide alarms, egress, or fire separation. That work is real construction, and it is usually most of the cost.

How local cities handle it

San Jose runs an AB 2533 ADU and JADU Legalization Program that it calls a "penalty-free path". Its FAQ says the program generally exempts owners from impact fees, capacity fees and connection charges, and that the process typically takes 4 to 6 months from a complete application. Unincorporated Santa Clara County runs its own AB 2533 program. Milpitas has a Safe ADU Legalization Program, and Mountain View has a Legalize Existing ADU program. In cities without a program, or whose code still shows an older cutoff date, the state law applies anyway. See the penalty rules by city for what each one charges outside this path.

How we handle it

We look at the unit and the paperwork first, so you know whether it qualifies, what proof you have, and what the inspector is likely to flag. Then we handle the drawings, the application and the corrective work through final inspection. For San Jose specifics, see legalizing an unpermitted unit as an ADU in San Jose.

Sources

• California Government Code Section 66311.7 (unpermitted ADUs built before 2020)
• California HCD: Accessory Dwelling Unit Handbook (March 2026)
• City of San Jose: AB 2533 ADU and JADU Legalization Program
• City of San Jose: AB 2533 Legalization FAQs
• County of Santa Clara: AB 2533 Legalization of Accessory Dwelling Units Program
• City of Milpitas: Safe ADU Legalization Program
• City of Mountain View: Legalize Existing ADU