You should contact your local (and, in the US, your state) tax authorities. These are the people who may require sales tax and returns from you. If you have not done the returns before, they should have no problem with getting you the forms and giving you some help to get them completed, so you can do them right. Keep notes of the numbers you call, the people you talk to, and the advice they give you, because mistakes might happen, and those notes may help you avoid being penalized for it if they do.