S.D. Codified Laws § 47-13B-15

A professional service corporation may adopt a pension, profit-sharing (whether cash or deferred), health and accident, insurance, or welfare plan for all or part of its employees including lay employees, providing that such plan does not require or result in the sharing of specific or identifiable fees with any lay employees and any payments made to lay employees or into any such plan in behalf of lay employees are based upon their compensation or length of service, or both, rather than the amount of fees or income received.