Open question: My wife becomes as outside firm, how much should set her paid for taxes of each pay cheque aside?

My wife is a new M.D. She works for a hospital and loads by the hour up. It receives once per month paying and receives the total amount of its pay cheque. No departures. How much they set aside from each pay cheque should and which kind of taxes does them, you must pay (APPROX.). Our tax bracket is in the 6 illustrations. I am not independent. Should it pay quarterly journal, therefore they do not add above? She was explained that a large error, which new doctors form they spend the complete pay cheque and terminate much above at the end of the year owe are, which they do not have.