Child support is a court-ordered payment to the custodial parent of a minor child after divorce or separation. Usually the amount is based on the income of both parents, the number of children, the expenses of the custodial parent, and any special needs of the child. It may also include health insurance, school tuition or other expenses, and may be reduced during periods of extended visitation such as summer vacations.

Every jurisdiction has its own regime for calculating support, and most also have websites that provide a general estimate of the amount. Common routines, however, are 1) what is called the income shares model, which calculates support by estimating the amount of support that would have been available to the children if the family had remained intact; 2) the percentage of income model, which affixes support a percentage of the income; or 3) the chart support method, which establishes a base support from a chart, taking into account the gross income of both parents, less special adjustments (such as support for children of a previous marriage).

A judge has latitude to deviate from the established formulas for child support as he or she deems necessary for reasons such as, but not limited to, education, medical care, or disparate income levels. Court will approve support arrangements they deem "fair and reasonable, so the amount that the state guidelines produce will not necessarily be the amount awarded by the court.

Unlike alimony, child support is not tax deductible to the payor, nor taxable to the payee.

Many states want to be harder on deadbeat parents who may face contempt-of-court charges and civil penalties. Criminal sanctions can include a jail sentence or a fine, but these punishments are used sparingly and for repeat violations. Prosecution may proceed on a misdemeanor or felony level, depending on the circumstances. A parent who crosses a state line to avoid paying support may face federal prosecution.

Wage withholding is the primary means of collecting child support. Withholding requires that the employer of the noncustodial parent send a percentage of the payors wages to the state or county collection agency, which forwards it to the custodial parent. Where the custodial parent receives federal public assistance, income withholding is mandatory. Interception of the obligor's federal tax return is another enforcement tool. Some $1.8 billion were collected in the first seven years after implementing a pilot of this requirement.

A parent cannot escape child support obligations by filing for bankruptcy. Child support is one of several debts that cannot be discharged.

Divorced parents set up separate households and almost always find their finances pinched. Very frequently, child support awards seem inadequate to the custodial parent and burdensome to the payor. One or the other parent, therefore, returns to court to seek modification of the award. An existing child support order may be modified if the child's needs or the paying parent's resources change. Back child support can be ordered if a modification or other order delays payment.

Some child support orders are automatically modified when certain conditions are met. For example, an escalation clause allows the child support amount to increase as the noncustodial parents income increases. A cost-of-living-adjustment (commonly referred to as a COLA) clause permits modification without a hearing when there is an increase in income coupled with inflation. The purpose of these clauses is to keep cases out of court. Courts usually do not approve automatic increases that are not based on an increase in income.

Child support normally ends when the child achieves a majority, which is usually 18, marries, or can support herself or himself. At the least it continues through high school graduation, and in some jurisdictions, may continue through college.