Code of Civil Procedure CCP § 1161.1
With respect to application of Section 1161 in cases of possession of commercial real property after default in the payment of rent:
(a) If the amount stated in the notice provided to the tenant pursuant to subdivision (2) of Section 1161 is clearly identified by the notice as an estimate and the amount claimed is not in fact correct, but it is determined upon the trial or other judicial determination that rent was owing, and the amount claimed in the notice was reasonably estimated, the tenant shall be subject to judgment for possession and the actual amount of rent and other sums found to be due. However, if (1) upon receipt of such a notice claiming an amount identified by the notice as an estimate, the tenant tenders to the landlord within the time for payment required by the notice, the amount which the tenant has reasonably estimated to be due and (2) if at trial it is determined that the amount of rent then due was the amount tendered by the tenant or a lesser amount, the tenant shall be deemed the prevailing party for all purposes. If the court determines that the amount so tendered by the tenant was less than the amount due, but was reasonably estimated, the tenant shall retain the right to possession if the tenant pays to the landlord within five days of the effective date of the judgment (1) the amount previously tendered if it had not been previously accepted, (2) the difference between the amount tendered and the amount determined by the court to be due, and (3) any other sums as ordered by the court.
(b) If the landlord accepts a partial payment of rent, including any payment pursuant to subdivision (a), after serving notice pursuant to Section 1161 , the landlord, without any further notice to the tenant, may commence and pursue an action under this chapter to recover the difference between the amount demanded in that notice and the payment actually received, and this shall be specified in the complaint.
(c) If the landlord accepts a partial payment of rent after filing the complaint pursuant to Section 1166 , the landlord’s acceptance of the partial payment is evidence only of that payment, without waiver of any rights or defenses of any of the parties. The landlord shall be entitled to amend the complaint to reflect the partial payment without creating a necessity for the filing of an additional answer or other responsive pleading by the tenant, and without prior leave of court, and such an amendment shall not delay the matter from proceeding. However, this subdivision shall apply only if the landlord provides actual notice to the tenant that acceptance of the partial rent payment does not constitute a waiver of any rights, including any right the landlord may have to recover possession of the property.
(d) “Commercial real property” as used in this section, means all real property in this state except dwelling units made subject to Chapter 2 (commencing with Section 1940 ) of Title 5 of Part 4 of Division 3 of the Civil Code, mobilehomes as defined in Section 798.3 of the Civil Code , or recreational vehicles as defined in Section 799.24 of the Civil Code .
(e) For the purposes of this section, there is a presumption affecting the burden of proof that the amount of rent claimed or tendered is reasonably estimated if, in relation to the amount determined to be due upon the trial or other judicial determination of that issue, the amount claimed or tendered was no more than 20 percent more or less than the amount determined to be due. However, if the rent due is contingent upon information primarily within the knowledge of the one party to the lease and that information has not been furnished to, or has not accurately been furnished to, the other party, the court shall consider that fact in determining the reasonableness of the amount of rent claimed or tendered pursuant to subdivision (a).