Streets and Highways Code § 6448

When all payments on a bond are made to the treasurer, he shall enter the same in his record of the bond and the lien of the assessment shall cease.

The treasurer shall forthwith notify the holder of the bond and call in the bond. When the bond has been presented and paid the treasurer shall enter in his record thereof the amount paid and the date of payment to the holder and shall cancel the bond and file it in his office.