Delta Motor Corporation (the respondent) is a motor vehicle manufacturer and distributor that has imported vehicle parts in the form of CKD (completely knocked down) kits from Adam Opel Aktiengesellschaft, Germany ('Opel') since 1987. For years, it paid customs duty calculated on the invoiced amount payable per kit. In 1997, a consultant advised that the invoiced amount had included not only the purchase price of the kit but also an unspecified charge by Opel for engineering, styling and tooling ('EST'). The respondent requested a refund of customs duty, claiming that the EST charge was not part of the price payable for a kit but rather a non-dutiable royalty. The appellant (SARS) refused the refund. The relationship between the parties was governed by three agreements: an assembly and distribution agreement, a trademark licence agreement, and a supply agreement. The EST charge remained relatively constant in amount and was not related to or calculated with reference to the cost, weight, number or value of components in a kit. It was payable in respect of every assembled vehicle actually sold, even if an assembled vehicle contained no components from an imported kit. A 1998 amendment to the agreements clarified that the EST charge comprised an engineering and styling portion (representing the royalty payable under the assembly and distribution agreement) and a tooling portion (covering rebilling of component tooling investment).