Bloomberg:

Square Inc., the mobile-payments company founded and led by Jack Dorsey, the interim chief executive officer of Twitter Inc., filed confidentially for an initial public offering, people with knowledge of the matter said.

Square has been working with Goldman Sachs Group Inc., Morgan Stanley and JPMorgan Chase & Co. on the IPO, said the people, who asked not to be identified because the process is private

This comes shortly after Square announced a payroll processing service and a real-time sales tracking application.