California Code, Health and Safety Code - HSC § 101335

The tax collector shall include the amounts of the assessments entered on the assessment roll pursuant to Section 101330 on bills for taxes levied against lots and parcels of land, and the assessments shall be listed separately on the tax bills.  Thereafter, the assessment amounts shall be collected at the same time and in the same manner as county taxes are collected.

If a county collects the assessments on behalf of a city, the county may deduct its reasonable costs incurred for its collections services before remitting the balance to the city treasury.