Going along with Zyphlin's questions, if a man has three wives and each wife has two other husbands, how would they work out filing their taxes? In order to file joint with each, they would have to file taxes at least three times. But then how would their taxes be calculated? What if they had to pay with two but got a refund with the other? These are legitimate questions. And they are not covered in any way by current tax laws because marriage functions around a person only having one spouse.