When you suspect the other parent's income has changed after your child support order has go through the court and there has been a final judgement, be very careful about going to file for motion to change the support. If you are wrong about the other parent's raise in income and it has in fact gone down, the judge may make an order to in fact, lower the current child support amount. Also, it may be that you are the support payer and have filed a motion to change the child support order amount, if in fact the other parent's income has lowered. In this case you will be ordered to pay more.
To find out whether the other parent's income has changed, you cane have someone (who is not in any way connected to your case and is an adult) serve a Request for Production of an Income and Expense Declaration After Judgment, and a Income and Expense Declaration to the other parent IF there has already been a final verdict made on your case.
The parent who receives these request forms will have 30 days once the papers are served to fill them out and return them. Meanwhile the other parent must send in copies of their most recent tax forms (both state and federal) so that they may be reviewed.