I Opened a Bank in Datang

The debtor, Li Shimin, owed Zhao Nanfeng 3 million taels of silver, with an annual interest rate of 500%, and the date of arrears, 590 AD! The debtor, Qin Qiong, owed Zhao Nanfeng 1.2 Million taels of silver, with an annual interest rate of 900%, and the date of arrears, 591 AD! The debtor, Cheng Yaojin, owes 500,000 taels, with an interest rate of 3000%, and the date of payment... With these IOUs in hand, Zhao Nanfeng became the richest man in the Tang Dynasty.