Dorsey, along with co-founder Jim McKelvey, developed a small Business platform to accept debit and credit card payments on a mobile device called Square, released in May 2010. The small, square-shaped device attaches to iPhone, iPad, iPod Touch, or Android devices via the headphone jack, and as a mini card reader allows a person to swipe their card, choose an amount to transfer to the recipient and then sign their name for confirmation. Square is also a system for sending paperless receipts via text message or email, and is available as a free app for iOS and Android OS. The company grew from 10 employees in December 2009 to over a hundred employees by June 2011. Square's office is located on Market Street in San Francisco. In September 2012, Business Insider magazine valued Square Inc. at US$3.2 billion. Dorsey is CEO of Square, Inc. On October 14, 2015, Square filed for an IPO to be listed on the New York Stock Exchange. As of that date, Dorsey owned 24.4% of the company.