Child support after a divorce is determined using state issued guidelines. These generally calculate the appropriate payment level as a percentage of the non-custodial parent's net income. However, a support order may be modified at the discretion of the court. For example, a person with a very low income might be required to simply pay flat dollar amount per month depending on the minimum support level in that state. Many people assume that when a child turns 18 payments will automatically stop. However, in many cases it is necessary for the non-custodial parent to contact the court to stop child support. Divorce agreements may also stipulate that support payments will continue while a child is attending college. Either parent has the ability to request a modification in child support if there is a significant change in financial circumstances. The custodial parent can enlist the aid of the state in collecting unpaid support.