California Code, Water Code - WAT § 52301

In all cases where it is provided in this division that bonds and interest coupons may be used in lieu of cash, and the entire amount of any bonds or coupons tendered is not required to complete the particular transaction, the county treasurer shall endorse thereon, as paid, the amount thereof which is tendered for payment or cancellation, and shall endorse on the unmatured coupons attached to such bond the amount for which the unmatured coupons are redeemable, the amount to be computed on the unpaid portion of the bond at the rate of interest provided in the bond.