Throughout the 21st century, money from all countries switched slowly from a paper and coin currency to an electronic one.  As corporations took governmental control over planets in other solar systems, individual currencies based on earth-bound countries became less relevant.  Rather than switching to currencies based on individual planets, CEOs and other corporate barons agreed on a system wherein money would be based solely on electronic banking.  This system trickled down to the civilians who populated the planets, and now money switches hands solely as numbers scanned across machines utilizing plastic cards.  When a person loses their card, they have absolutely no method of spending money, and must get a new one from their corporate bank.