Purchases from Amazon.com in states that don't have an Amazon.com presence (California in this instance) generally are taxed. It's called "Use Tax", and it is

Purchases from Amazon.com in states that don't have an Amazon.com presence (California in this instance) generally are taxed. It's called "Use Tax", and it is your responsibility as a taxpayer to report it and pay it. The Californian government wants Amazon.com to collect a sales tax, instead the use tax. Either way the purchases are taxed, unless of course you choose to dodge your taxes...