Cal. Rev. & Tax. Code § 4337

When payment of delinquent taxes in installments on any property was started under any provision of law and payment of delinquent taxes in installments on the property is later started after default in payment, there shall be credited on the amount payable the total amount of back taxes paid during the course of the defaulted plan or plans, including an allowance for interest paid pursuant to Section 4221. This credit is in addition to and not a substitute for the payment of any part of any installment payable and shall be allowed after the first installment is paid.