回复：请教老猫，前夫为少付抚养费，隐瞒收入，该怎么办？

If you believe his income changes significently, you can file a petition to modify child support. both of you need to fill out financial disclosure form, include tax returns. Since you don't know beforehand what you want to ask, you can opt to use state guideline. The new amount will start on the petition date. no retros.

tax evasion is a different matter. if he has a way to pay less tax, legal or illegal, that's his business. better dealing with child support first.