Samsung Securities typed the wrong number and issued $100B of phantom shares

On April 6, 2018, an employee at Samsung Securities, one of South Korea's largest brokerages, attempted to pay a dividend of about 1,000 won (roughly US$1) to approximately 2,000 employees in the company's employee stock ownership plan. Instead, the employee mistakenly issued 2.8 billion shares — worth approximately US$100 billion (112.6 trillion won), about 30 times the company's entire market capitalization.

The company noticed the error 37 minutes later. By then, 16 employees had already sold the mistakenly issued shares, and some had done so despite warnings from the company. Each seller could have pocketed up to US$9 million. Samsung Securities' stock fell 11% in a single day.

The National Pension Service, with 136 trillion won invested in the Korean market, immediately halted trading with Samsung Securities. The Financial Supervisory Service said the incident undermined trust in the Korean capital market. Samsung Securities said it would file criminal lawsuits against the employees who sold, and prosecutors raided the firm's offices in May 2018. A later watchdog probe found that 21 employees had traded or attempted to sell the phantom shares. The error also involved illegal naked short selling, which the system was not supposed to allow.