The situation is obviously pretty complicated, with lost of players involved.
Your question is whether a tax deposit was "illegal." Well, not as phrased -- depending on what is actually going on, any existing orders, where you are procedurally (you say he is your "ex"), etc., you may, or may not, have a claim to the money.
The "most effective way" to go about any motion is to have your ducks in a row (your evidence assembled) and if the other side will not be reasonable, present it, logically and as organized as possible, to the court.
On the paycheck question, sure! I suggest a subpoena to the employer requiring disclosure of all sums paid, and to what accounts. My guess is that you will find out all kinds of exciting things.
Answered on May 11th, 2014 at 10:09 PM