Cal. Sts. & High. Code § 18125

At any time after the date of sale and prior to the issuance and delivery of a deed to the land sold, any land sold under the provisions of this chapter may be redeemed by the payment to the tax collector of the amount for which the land was sold, with an additional penalty of 1 per cent per month of said amount together with such other penalties as may be payable as provided in this chapter. Said 1 per cent penalties shall be added on the first day of each month following the date of the sale of the land.