Cal. Rev. & Tax. Code § 4106.1
With the approval of the board of supervisors the tax collector may establish a procedure for making and preserving a record of individual redemption and installment payments. When such a procedure is established, receipts for redemption and installment payments made by mail shall only be issued when a receipt is requested by the person making payment. The redemption certificate or installment plan form shall contain a statement that receipts will not be issued for payments made by mail unless a receipt is requested by the person making payment, and an appropriate place in which the taxpayer may request a receipt shall be provided on the redemption certificate and the installment plan form. Receipts requested shall be furnished without cost to the taxpayer.
Ca. Rev. and Tax. Code § 4106.1