S.D. Codified Laws § 58-14-16.17

A ceding insurer shall take steps to diversify the ceding insurer's reinsurance program. A domestic ceding insurer shall notify the director within thirty days after ceding to any single assuming insurer, or group of affiliated assuming insurers, more than twenty percent of the ceding insurer's gross written premium in the prior calendar year, or after the ceding insurer has determined that the reinsurance ceded to any single assuming insurer, or group of affiliated assuming insurers, is likely to exceed this limit. The notification shall demonstrate the exposure is safely managed by the domestic ceding insurer.