The amount owed for child support by the non-custodial parent is determined the state. Therefore, each state has their own guidelines for this matter. Gross income or net income could be used in the formula for calculating child support. Either net income or gross income is used as a part of their formula. Typically, an important element in most cases is the percentage of income that each parent was able to put into the marriage.
If a parent receives non-wage benefits from their employer, then it could be considered income. An example for instance is having access to a company car to do business.
If the parent ordered to pay child support is already paying support for previous divorce, then typically that amount will be deducted from their income. This is assuming that the support payments were organized in court, and not in an uncontested divorce where an arrangement was made between the two spouses. Also included is the child's health insurance costs. Should any out of pocket medical expenses incur, then more child support could be added.
If the child has any special needs, then this may increase child support as well. For instance, if he or she is handicapped, is gifted, or needs special education, then the basic support would call for covering at least a portion of these expenses. Visitation expenses are generally divided between the two parents.
The more time the non-custodial parent gets to spend with their children, the more child support he or she will have to pay. In situations of extensive visitation or shared custody, the amount paid will be less.
The state's guidelines ultimately dictate how much child support is awarded. However, this amount could be decreased or increased if extenuating circumstances are in place. A judicial determination will have to be made in this regard in order to overrule the guidelines.
Can the terms of an existing child support change? The answer is yes, assuming that the two parents can agree to the modifications. Though, the judge will have to approve the modifications before they can become official. If only one parent wants changes, then a hearing in court will take place. Here, an argument can be made as to why the terms should be altered. Typically, the courts won't allow for changes to occur unless something rather substantial has taken place. For instance, if for one reason or another you couldn't afford to make the payments, then it might change. On the other hand, if your pay increases because you got a better job, your payments could increase.