California Code, Revenue and Taxation Code - RTC § 2505

(a) Except as provided in subdivision (b), the tax collector or treasurer for any city or county may in his or her discretion accept negotiable paper in payment of any tax, or assessment, or on a redemption.

(b) The tax collector of a county shall accept a certificate of eligibility to pay all or any part of any ad valorem property tax, special assessment, or other charge or user fee appearing on the county tax bill.  The tax collector, treasurer, or other official charged with the duty of collecting taxes for a chartered city which levies and collects its own property taxes shall accept a certificate of eligibility to pay all or any part of any ad valorem property tax, special assessment, or other charge or user fee appearing on the tax bill of such city.  A certificate for partial payment shall not be accepted unless accompanied by an amount sufficient to fully pay the remaining ad valorem property taxes, special assessment, or other charge or fee appearing on the respective tax bill installment.

(c) For the 1978-79 fiscal year and thereafter, except as to those amounts which can be paid by a certificate pursuant to subdivision (c), the tax collector shall not accept a certificate of eligibility to pay all or part of any installment if tendered after the delinquency date thereof, unless accompanied by an amount sufficient to fully pay any delinquent taxes, assessments, costs, penalties, interest, fees or other charges resulting from the delinquency or delinquencies.

(d) In no event shall a certificate of eligibility be accepted later than the expiration date designated thereon.