Determining the amount of child support that one parent pays to the other can be one of the most bitterly-contested phases of a divorce. If the couple can't work out an amount on their own and the matter goes to a family court judge, the amount of child support is usually based on the income of each parent, how much time the children are spending with the parent with primary custody and the needs of the child(ren) involved.
The best interests of the child are mandated to be the primary factor for any judge deciding issues involving them. Their standard of living should remain relatively comparable between the home where they live with their custodial parent and that of their non-custodial parent.
Child support is intended to pay for the housing, food, education, clothing, health care and other necessities for raising a child. It should also cover the normal needs that children have, such as toys and books. If a child takes music or dance lessons, is involved in sports or has special needs, child support may be ordered to help pay for those things.
The parent receiving child support is not allowed to use it for anything that doesn't help the child. They can't use it for vacations that their kids aren't included in or for things like spa days. That's considered a misappropriation of the support.
If you believe that your ex is using all or part of your child support payments for anything other than the support, health and well-being of your child, don't just withhold payments. That can get you in serious legal jeopardy. Tell your attorney so that he or she can initiate the appropriate action with the court.
Source: The Good Men Project, "This Is What Child Support IS…And Is NOT," March 31, 2017