Szombatfalvy began his stock trading career with 6,000 Swedish Kronor (Crowns) in the mid-1960s. In 1971 Szombatfalvy resigned from his then employment with the Finance Department at Swedish Shell to begin full-time trading in shares. By the time he had celebrated his 60th birthday in 1987, Szombatfalvy's wealth was estimated at 250 million Swedish Kronor, at which point he decided to stop active management of his stock. In 2013, through successful placements of shares on the Swedish Stock Exchange, he had reportedly amassed a personal fortune of one billion Kronor. His private fortune was invested mainly in 10 million shares in the listed Swedish real-estate company, Castellum AB.
