S.D. Codified Laws § 25-7-6.6
Gross income from a business, profession, farming, rentals, royalties, estates, trusts, or other sources, are the net profits or gain, or net losses shown on any or all schedules filed as part of the parents' federal income tax returns or as part of any federal income tax returns for any business with which he is associated, except that the court may allow or disallow deductions for federal income taxation purposes which do not require the expenditure of cash, including, but not limited to, depreciation or depletion allowances, and may further consider the extent to which household expenses, automobile expenses, and related items are deductible or partially deductible for income tax purposes. In the event a court disallows depreciation, it may consider necessary capital expenditures which enhance the parent's current income for child support purposes.
SDCL 25-7-6.6