Gov. Code, § 29142

Notwithstanding any other provision of law, when taxes or assessments are collected by the county for any special district, or zone or improvement district thereof, but excluding a school district, the board of supervisors may provide for a collection fee for such services which when collected shall belong to the county and shall be deposited to the credit of the general fund, and shall cover the expense and compensation of such officials of the county in the collection of such taxes and of the interest or penalties thereon, subject to the following:

(a) For taxes covering debt service requirements on any bond or bonds authorized and issued by any such special district, the tax rate fixed to raise such amounts may be fixed by the board of supervisors to include also a percentage of such amounts up to one-fourth of 1 percent thereof.

(b) For taxes covering all purposes of such special districts, other than debt service requirements on bonds, the amount of the collection fees, if any, to be charged by the county shall be fixed by agreement between the board of supervisors and the governing board of such special district and shall not exceed one-fourth of 1 percent of all money collected.