Your client sounds like a musician, and since I am also a professional musician, I can answer this one. You need to register as a business with the state in which you live. Once you do, you'll need a seller's permit or license or whatever other requirement your state has. At that point, your client will register with the state to file those taxes. I think the best idea is for your client to work with an accounting professional to get all of this stuff set up and hten you can automate from there. All the best.