If you change "do" to "done", it's grammatical, but I wouldn't use a tag question in this instance. If you're required to for your lesson, I suppose it should be "You mustn't have done it, must you?", but it sounds very strange to me.
June 5, 2013
There's nothing you can put in that blank to make that a good sentence. "You mustn't have do it" doesn't make sense.