Cal. Welf. and Inst. Code § 279
The board of supervisors may impose a service charge at a uniform rate sufficient to defray the cost of services of the probation officer or other officer designated to act as trustee, not exceeding 2 percent of the amount collected, in addition to the payments made under subdivision (a), (c), (d), or (f) of Section 276. However, a service charge may not be imposed for services relating to child support.
The service charge imposed in relation to payments under subdivision (c) of Section 276 shall be imposed only for payments made by probationers, and the service charge imposed in relation to payments made under subdivision (f) of Section 276 shall be imposed only for cases similar to those listed in subdivision (a), (c), or (d) of that section.
When the payments are ordered by the court, the payment of the service charge shall be included in the order. All proceeds shall be deposited in the general fund of the county.
Ca. Welf. and Inst. Code § 279