S.D. Codified Laws § 50-11-19.3
When determining the amount of the registration tax imposed by § 50-11-19 on homebuilt aircraft, a credit for South Dakota sales tax and South Dakota use tax that was paid by the applicant on any purchase of aircraft kits, engines, instruments, and other parts and components used in the construction of the homebuilt aircraft is permitted. The applicant shall provide proof of the South Dakota sales tax and the South Dakota use tax that was paid by the applicant and is eligible for credit by providing any invoice, receipt, or other document that shows the payment of South Dakota sales tax and South Dakota use tax. The amount of the credit permitted by this section may not be greater than the registration tax imposed by § 50-11-19 on the homebuilt aircraft. No credit is permitted for any South Dakota sales tax or South Dakota use tax that was paid more than five years before the date of the application for registration of the homebuilt aircraft.
SDCL 50-11-19.3