Click on tab to return FAQs listings. Frequently Asked Questions Topic: Calculate Support Payments Q:How is the support obligation amount calculated? Each state has a child support guideline. The District of Columbia Child Support guidelines are calculated using data on the non-custodial parent (NCP) and custodial parent (CP). The custodial parent is the person with whom the child resides. The non-custodial parent is the parent with whom the child does not requlary reside. The information used in calculating the support obligation includes income, proof of insurance medical coverage, child care expenses, age of the children, and the ncp's other child support cases.