The Illinois Child Support Data Sheet (also referred to as the “CSP”) is an official document used in the state of Illinois to calculate child support payments. It is a two-page form that requires information about the custodial and non-custodial parents, their incomes, and the number of children they have. The CSP is used by the courts to determine the amount of child support payments that should be made. There are two different types of Illinois Child Support Data Sheet: the initial CSP, which is used in the initial court proceedings, and the modified CSP, which is used when there are changes in either parent’s income or the number of children. The CSP is also used to calculate any additional payments that may be due, such as medical and dental expenses.