S.D. Codified Laws § 25-7-6.14
If the child resides with the obligor six or more nights in a month pursuant to a custody order, the court may, if deemed appropriate under the circumstances, grant an abatement of not less than thirty-eight percent nor more than sixty-six percent of the basic child support obligation for the nights the child resides with the obligor. It shall be presumed that the parenting time is exercised.
In deciding whether an abatement is appropriate, the court or child support referee shall consider the fixed obligations of the custodial parent that are attributable to the child and to the increased non-duplicated costs of the noncustodial parent that are associated with the child's time with the noncustodial parent. The burden is on the noncustodial parent to demonstrate the increased costs that the noncustodial parent incurs for non-duplicated fixed expenditures, including routine clothing costs, costs for extra-curricular activities, school supplies, and other similar non-duplicated fixed expenditures.
The order granting the abatement must specify the number of nights that the abatement is allowed and the amount of the abatement. To calculate an abatement, the court or child support referee shall:
No abatement may exceed the child support cross credit allowed under § 25-7-6.27.
If the noncustodial parent does not exercise the extended parenting time during a particular year, the noncustodial parent is required to repay the abated amount of child support to the custodial parent.
SDCL 25-7-6.14