If a person ordered to pay child support were to then have the child for whom support was ordered living in his house, then he would have a defense to the child support obligation. In other words, since the point of child support is to provide housing and groceries for the child, if you and dad now live together and are providing housing and groceries for the child, then he technically does not owe child support. The problem comes in when the child support is withheld from the obligor’s paycheck. The order for child support probably has language describing that child support ends if you marry. So you could show the employer the marriage certificate and the order, and that might be enough. If the employer is not comfortable with that-because the employer is ORDERED to withhold child support, then a Motion to Modify Child Support will be necessary.