Sts. & Hy. Code, § 6442

If any installment of the principal of the unpaid assessment or of interest thereon is not paid to the treasurer on or before the due date of June 1st or December 1st, as the case may be, next preceding the date upon which the coupons representing it are payable to the bondholder, the treasurer shall, after the close of business on the due date, add to the principal or interest so delinquent a penalty of 2 percent of the total amount of such delinquency, and at the beginning of the business on the first day of each succeeding month until such delinquent payment and all penalties thereon are fully paid, he shall add an additional penalty of 2 percent of the amount of such delinquency. The treasurer shall collect such penalties with and as a part of the delinquent payment. Except as hereinafter provided, the 2-percent penalty first imposed and all subsequent penalties shall be paid to the holder of the bond along with and as a part of such defaulted payment. The legislative body conducting the proceedings may elect, in the resolution of intention, to have the treasurer retain the first 2-percent penalty as a cost of servicing the delinquency. In such case, the following sentence shall be substituted for the last sentence of the default clause in the bond form, as set forth in Section 6460: “The 2-percent penalty first imposed shall be retained by the treasurer as a cost of servicing the delinquency and all subsequent penalties shall be paid to the holder of the bond along with and as a part of such defaulted payment.”