In states with sales taxes, if you buy something from an out-of-state retailer and don’t pay taxes, you are supposed to pay those taxes when you file your state tax return, said Neal Osten, director the Washington office of the National Conference of State Legislatures.

Only Delaware, Montana, New Hampshire and Oregon have no sales tax. Alaska has no state sales tax but does have local ones.

Unpaid sales taxes are usually referred to as “use taxes” on state income tax returns. Use taxes apply to purchases made over Internet, from catalogs, television and radio ads and purchases made directly from out-of-state companies. State officials, however, complain that few people pay these taxes, Olsten said.

“I do know about three people that comply with that,” says Sen. Mike Enzi, R-Wyo., the main sponsor of the Senate bill.

Enzi’s bill would empower states to require businesses to collect taxes for products they sell on the Internet, in catalogs and through radio and TV ads. Under the bill, the sales taxes would be sent to the states where a shopper lives.