The court can order child support in essentially every case where there are children involved, whether it is a divorce case with children or a paternity case. Once the court orders child support, that can be changed until the children are 18 and out of high school. According to the Balance, there are several factors that govern the modification of child support. 

The most common things are changes in the party’s incomes. When incomes go up or down, that can form a basis to modify child support. Another common basis to modify child support is when you have got multiple children, say two children, and then the first one turns 18 and graduates high school. Usually, there should be a lower child support amount for only one child. Another thing that can change or influence the child support amount are when there are changes in child care expenses or medical insurance premiums. 

Since those factors influence the child support amount, when the cost of medical insurance or the cost of childcare expenses changes, the child support amount can also change. You do not seek a modification of child support unless when you run the child support guideline calculation. That is when the child support amount would change by 15% or more from the current child support amount. If you do not have a 15% or more change, the court will usually find that there is not a sufficient change in circumstances to modify child support. 

One thing that is also important is that there may be no retroactive child support modifications. You may have to seek the modification of child support immediately when the change of circumstances occurs.