Cal. Rev. & Tax. Code § 41024

Every service user in this state is liable for the surcharges until they have been paid to this state, except that payment to a service supplier registered under this part is sufficient to relieve the service user from further liability for the surcharges.

Any surcharge collected from a service user that has not been remitted to the department shall be deemed a debt owed to the state by the person required to collect and remit that surcharge. Nothing in this part shall impose any obligation upon a service supplier to take any legal action to enforce the collection of the surcharges imposed by this part. The service supplier shall provide the department with amounts uncollected which total three dollars ($3) or more on a cumulative basis with respect to a single service user along with the names, addresses, and reasons of the service users refusing to pay the surcharges imposed by this part.