Section 656 - Computation of parental support obligation(a) Except in situations where there is shared or split physical custody, the total child support obligation shall be divided between the parents in proportion to their respective available incomes and the noncustodial parent shall be ordered to pay, in money, his or her share of the total support obligation to the custodial parent. The custodial parent shall be presumed to spend his or her share directly on the child.(b) If the noncustodial parent's available income is less than the lowest income figure in the support guideline adopted under section 654 of this title or is less than the self-support reserve, the court shall use its discretion to determine support using the factors in section 659 of this title and shall require payment of a nominal support amount.(c) If the noncustodial parent's available income is greater than the self-support reserve but payment of a child support order based on application of the guideline would reduce the noncustodial parent's income below the self-support reserve, the noncustodial parent's share of the total support obligation shall be presumed to be the difference between the self-support reserve and his or her available income. If the noncustodial parent owes arrears to the custodial parent, the court shall not order the payment of arrears in an amount that, by itself or in combination with the noncustodial parent's share of the total support obligation, would reduce the noncustodial parent's income below the self-support reserve, unless the custodial parent can show good cause why the payment of arrears should be ordered despite the fact that such an order would drop the noncustodial parent's income below the self-support reserve. Such arrears shall remain the responsibility of the noncustodial parent and be subject to repayment at a time when the noncustodial parent's income is above the self-support reserve.(d) The court may use its discretion in determining child support in circumstances where combined available income exceeds the uppermost levels of the support guideline adopted under section 654 of this title.Added 1985, No. 180 (Adj. Sess.), § 4, eff. 4/1/1987; amended 1987, No. 54, § 5, eff. 5/15/1987; 1989, No. 220 (Adj. Sess.), § 18; 2003, No. 159 (Adj. Sess.) , § 1.