S.D. Codified Laws § 32-5-126
The department may provide, to an owner of any fleet of fifty or more trailers, registrations and license plates for the trailers which are valid for a period of not more than seven consecutive years. Such registered trailers are exempt from the requirements of an annual registration as provided by this chapter. The owner of such a fleet shall make application directly to the department. The owner shall pay at the time of registration for each trailer the registration fee as provided by § 32-5-8 for the entire registration period. The owner shall pay any registration fee increases which occur during the period for which the trailers are registered. All fees collected shall be deposited in the local government highway and bridge fund created pursuant to § 32-11-34. The department may cancel the registrations and license plates at any time for any reason.
SDCL 32-5-126