The Medici Bank bypassed religious bans on interest by disguising loans as currency exchanges

Founded in 1397, the Medici Bank became the most powerful financial institution in Europe by mastering the 'bill of exchange.' Because the Church viewed charging interest on loans as a sin, the Medici disguised their profits as fees for converting one currency to another across their ten European branches. This allowed them to charge effectively between 5 and 15 percent interest while remaining in good standing with the Papacy.