Cal. RTC § 23222

(a) If a taxpayer commences to do business in this state during its first taxable year its tax for that year shall be adjusted upon the basis of the net income received during that taxable year, at the rate applicable to that year, a credit being allowed for the prepayment of the minimum tax. The return for the first taxable year, which shall be filed within 2 months and 15 days after the close of that year, shall also be the basis for the tax of said taxpayer for its second taxable year, if its first taxable year is a period of 12 months. In every case in which the first taxable year of a taxpayer constitutes a period of less than 12 months, or in which a taxpayer does business for a period of less than 12 months during its first taxable year, said taxpayer shall pay as a prepayment of the tax for its second taxable year a tax based on the income for the first taxable year computed under the law and at the rate applicable to the second taxable year, the same to be due and payable at the same times and in the same manner as if that amount were the entire amount of its tax for that year; and upon the filing of its tax return within 2 months and 15 days after the close of the second taxable year it shall pay a tax for said year, at the rate applicable to that year, based upon its net income received during that year, allowing a credit for the prepayment; but in no event, except as provided in Section 23332, shall the tax for the second taxable year be less than the amount of the prepayment for that year, and said return for its second taxable year shall also be the basis for the tax of said taxpayer for its third taxable year, if the second taxable year constitutes a period of 12 months.

(b) The provisions of subdivision (a) shall be applicable only if a taxpayer commenced doing business in this state before January 1, 1972.