Matt Cardy/Getty Images

The Amazon Swansea fulfilment centre in Swansea, Wales.

Amazon became a big player in the retail marketplace by offering the same products at a local store, for less.

Part of this had to do with the fact that they didn't have to charge customers sales tax.

Well, that all changes this week. On September 15, Amazon will start charging California residents state sales tax, which can be as high as 9.75 percent in some areas.

Guest:

Matt DeBord, KPCC business reporter