回複：請教老貓，前夫為少付撫養費，隱瞞收入，該怎麽辦？

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.