California Code, Government Code - GOV § 16771

Upon the payment of any such bond or coupon, the State Treasurer, or the state fiscal agent, or other duly authorized agent, shall cancel the same in a manner to indicate the payment.  The State Treasurer, or state fiscal agents, or other duly authorized agents, shall also on the respective dates of maturity of any such bonds that have been executed but remain unsold, cancel the same in a manner to indicate cancellation and on the respective due dates of all coupons attached to any such bond remaining unsold, shall detach all coupons the due date of which has been reached, and cancel them in the same manner as provided for the cancellation of bonds remaining unsold.