If you purchase cigarettes online, you may want to watch your mailbox.

That’s because the State's Revenue Department is sending letters to online cigarette shoppers, telling them to stop, or pay the $1.77 tax that's now if effect.

So far, the department says it's sent more than a thousand of those letters.

The state gets the names from internet cigarette vendors, after notifying 75 of them that a federal law makes it their responsibility to ensure Wisconsin gets the tax money.

The Revenue Department says smokers could be billed if their names show up as repeat buyers.