Back child support is the total payment the non-custodial parent must pay after having defaulted on child support payments for a period of time. For instance, if a mother is ordered to pay the custodial father $300 a month, but defaults for an entire year, she may be forced to pay the custodial father $3,600 in back child support. In some cases, the non-custodial parent may have to pay additional fines or fees if they have defaulted on child support payments. Speaking with an attorney can help both custodial and non-custodial parents understand more about back child support and determine whether they are eligible for it as well. Non-custodial parents who owe back child support could be forced to spend time in jail, or could have their wages or income tax returns garnished. An attorney can have the case reviewed if situations have changed, making it difficult for the custodial parent to make the child support payments.