I assume my ex-spouse gets bonus and commissions in addition to a yearly salary. How do I go about to request a copy of his W2 every year to collect?

In Wisconsin, there is a state law that when there is a child support or family support order in place, there must be an annual exchange of tax information to verify incomes. If your ex refuses to provide this information, file a contempt motion. There is also a law in this state that presumes a substantial change of circumstances sufficient to modify support after 33 months from the time the last support order was put into effect.