Cal. Rev. & Tax. Code § 2607

The entire tax on real property may be paid when the first installment is due and payable or at any time thereafter until the properties on the current roll become tax defaulted. The second installment may be paid separately only if the first installment has been paid. The tax collector shall accept payment of current year taxes even though prior year delinquencies on the real property may exist. The acceptance of that payment shall not affect the validity of any sale in satisfaction of a lien for defaulted taxes.