Note: The County of San Mateo had a local pilot Accessory Dwelling Unit (ADU) Amnesty Program between 2019 and 2022. That program has been discontinued, and the County has no local ADU Amnesty Program. 

However, in 2024 the California Legislature adopted AB 2533, a new law that provides some amnesty provisions for eligible ADUs created without permits prior to 2020. The full text of the law is in Government Code Section 66323.  

For an unpermitted ADU or JADU constructed before January 1, 2020, the relief provided by AB 2533 includes the following:  

• A local agency shall not deny a permit for an ADU or JADU that is in violation of California building standards (codes) or does not comply with any local ordinance regulating ADUs or JADUs. 

• The property owner applying for a permit to legalize an unpermitted ADU or JADU shall not be required to pay impact fees or connection or capacity charges except where utility infrastructure is required to comply with Health and Safety Code section 17920.3. 

• The local agency is prohibited from penalizing an applicant for having the unpermitted unit, and the local agency is required to approve necessary permits to correct noncompliance with health and safety standards. 

• Upon receiving an application for permit to legalize an unpermitted ADU or JADU, an inspector from the local agency may inspect the unit for compliance with Health and Safety standards and provide recommendations to comply with these standards. 

Other provisions and exceptions are incorporated in the law. Eligibility for the amnesty provided by AB 2533 depends on the type of ADU or JADU, the date of the ADUs construction, and various other factors. The process of applying for amnesty for an unpermitted unit is the same as an application for a new ADU, as described here: San Mateo County Accessory Dwelling Unit Permitting