Cal. Civ. Code § 799.40

799.40 Eviction actions.
(1) When commenced. A civil action of eviction may be commenced by a person entitled to the possession of real property, or by that person’s agent authorized in writing, to remove therefrom any person who is not entitled to either the possession or occupancy of such real property.
(1g) Notice terminating tenancy. If a landlord gives a notice terminating tenancy under s. 704.16, 704.17, or 704.19 through certified mail in accordance with s. 704.21 (1) (d), proof of certified mailing from the United States post office shall be sufficient to establish that proper notice has been provided for the purpose of filing a complaint or otherwise demonstrating that proper notice has been given in an eviction action, and an affidavit of service may not be requested to establish that proper notice has been provided.
(1m) Acceptance of rent or other payment. If a landlord commences an action under this section against a tenant whose tenancy has been terminated for failure to pay rent or for any other reason, the action under this section may not be dismissed because the landlord accepts past due rent or any other payment from the tenant after serving notice of default or after commencing the action.
(1s) No waiver by landlord or tenant. It shall not be a defense to an action of eviction or a claim for damages that the landlord or tenant has previously waived any violation or breach of any of the terms of the rental agreement including, but not limited to, the acceptance of rent or that a custom or practice occurred or developed between the parties in connection with the rental agreement so as to waive or lessen the right of the landlord or tenant to insist upon strict performance of the terms of the rental agreement.
(2) Joinder of other claims. The plaintiff may join with the claim for restitution of the premises any other claim against the defendant arising out of the defendant’s possession or occupancy of the premises.
(3) Exception. Nothing in this section shall affect ss. 704.09 (4) and 704.19.
(4) Stay of proceeding.
(a) The court shall stay the proceedings in a civil action of eviction if the tenant applies for emergency assistance under s. 49.138, except that no stay may be granted under this paragraph after a writ of restitution has been issued in the proceedings. If a stay is granted, the tenant shall inform the court of the outcome of the determination of eligibility for emergency assistance. The stay remains in effect until the tenant’s eligibility for emergency assistance is determined and, if the tenant is determined to be eligible, until the tenant receives the emergency assistance, except that the stay may not remain in effect for more than 10 working days, as defined in s. 227.01 (14).
(b) The court shall stay the proceedings in a civil action of eviction against a foreclosed homeowner, as defined in s. 846.40 (1) (b), under the circumstances and as provided in s. 846.40 (9).