Five hundred years ago, navigating the Strait of Hormuz required a permit known as a “Kartaz.” Implemented by the Portuguese in Hormuz, this system wasn’t simply a customs fee, but a comprehensive control mechanism. The Kartaz functioned as a mandatory license regulating all maritime traffic, effectively controlling both trade and naval security in the region. It combined elements of customs duties and tribute collection with Portugal’s military strength to exert dominance. This system allowed the Portuguese to monitor and influence commerce passing through this vital waterway. The Kartaz offers insight into historical methods of maritime regulation and power projection. It demonstrates how strategic chokepoints were managed and controlled in the early modern period.