I have an auto-repair shop in California. We install tinted windows in various vehicles upon client request. Is this job subject to sales tax in California?

The short answer is that tinted windows are subject to sales tax in California. However, the party that collects that sales tax depends on the nature of the transaction. Specifically, if the tinted film is not itemized on the invoice and the retail fair value is 10% or less of the total charge, the auto-repair shop is treated as the consumer and must remit sales tax to the supplier. However, if the cost of tinted film is more than 10% of the total charge, the item must be segregated and sales tax must be collected as referenced in California State Code Section 315.0330.