Cal. Civ. Code § 9

  § 9. Application for adjustment of initial legal regulated rent. a.
The owner or tenant of a housing accommodation described in paragraph
one or two of subdivision b of section six may, within sixty days of the
local effective date of this act or the commencement of the first
tenancy thereafter, whichever is later, file with the state division of
housing and community renewal an application for adjustment of the
initial legal regulated rent for such housing accommodation. The state
division of housing and community renewal may adjust such initial legal
regulated rent upon a finding that the presence of unique or peculiar
circumstances materially affecting the initial legal regulated rent has
resulted in a rent which is substantially different from the rents
generally prevailing in the same area for substantially similar housing
accommodations.
  b. The tenant of a housing accommodation described in paragraph two,
subdivision b, of section six may file with the state division of
housing and community renewal, within ninety days after notice has been
received pursuant to subdivision c of this section, an application for
adjustment of the initial legal regulated rent for such housing
accommodation. Such tenant need only allege that such rent is in excess
of the fair market rent and shall present such facts which, to the best
of his information and belief, support such allegation. The rent
guidelines board shall promulgate as soon as practicable after its
creation guidelines for the determination of fair market rents for
housing accommodations as to which an application may be made pursuant
to this subdivision. In rendering a determination on an application
filed pursuant to this subdivision b, the state division of housing and
community renewal shall be guided by such guidelines. Where the state
division of housing and community renewal has determined that the rent
charged is in excess of the fair market rent it shall order a refund, of
any excess paid since January first, nineteen hundred seventy-four or
the date of the commencement of the tenancy, whichever is later. Such
refund shall be made by the landlord in cash or as a credit against
future rents over a period not in excess of six months.
  c. Upon receipt of any application filed pursuant to this section
nine, the state division of housing and community renewal shall notify
the owner or tenant, as the case may be, and provide a copy to him of
such application. Such owner or tenant shall be afforded a reasonable
opportunity to respond to the application. A hearing may be held upon
the request of either party, or the division may hold a hearing on its
own motion. The division shall issue a written opinion to both the
tenant and the owner upon rendering its determination.
  d. Within thirty days after the local effective date of this act the
owner of housing accommodations described in paragraph two of
subdivision b of section six, as to which an emergency has been declared
pursuant to this act, shall give notice in writing by certified mail to
the tenant of each such housing accommodation on a form prescribed by
the state division of housing and community renewal of the initial legal
regulated rent for such housing accommodation and of such tenant's right
to file an application for adjustment of the initial legal regulated
rent of such housing accommodation.
  e. The initial legal regulated rents for housing accommodations in a
city having a population of one million or more shall be subject to
adjustment in accordance with the provisions of the New York city rent
stabilization law as amended.