Yes, sales tax still applies.
The California sales tax law can be found here:
California Revenue and Taxation Code
The relevant portions are as follows:
6006. "Sale" means and includes:
(g) Any lease of tangible personal property in any manner or by
any means whatsoever, for a consideration, ...
6010. "Purchase" means and includes:
(e) Any lease of tangible personal property in any manner or by
any means whatsoever...
6011. (a) "Sales price" means the total amount for which tangible
personal property is sold or leased or rented, as the case may be,
valued in money, whether paid in money or otherwise...
6012. (a) "Gross receipts" mean the total amount of the sale or
lease or rental price, as the case may be, of the retail sales of
retailers, valued in money, whether received in money or otherwise,
without any deduction on account of any of the following:
... (b) The total amount of the sale or lease or rental price
all of the following:
(1) Any services that are a part of the sale....
Basically, the law says that the _total_ cost of the lease is taxable.
If it's a cost of the lease, it's taxable. It makes no difference
whether a company charges $X for a lease and $Y for excess mileage or
whether it charges $(X+Y) for the lease and charges for no excess
mileage, it's the total lease cost that matters.
What Respree-ga says below is also accurate. The company that sold you
the lease is who hands over the tax money to the state, and what it
hands over is based on its gross revenue. Again, it doesn't matter if
that revenue comes from a regular lease payment or from an "excess
mileage charge," it's still taxable revenue.
I hope this helps, even if it might not be the news you were looking
I went to http://www.findlaw.com and followed links to find the
California tax statuetes.