Uber application logo is seen on a screen in front of taxi board in Ankara, Turkey on August 31, 2018.

The ride-hailing company filed the confidential paperwork on Thursday, in lock-step with its smaller U.S. rival, Lyft Inc, which also announced on Thursday it had filed for an IPO, setting the stage for one of the biggest technology listings ever.

Uber Technologies Inc has filed paperwork for an initial public offering, according to three people with knowledge of the matter, taking a step closer to a key milestone for one of the most closely watched and controversial companies in Silicon Valley.

The simultaneous filings extend the protracted battle between Uber and Lyft, which as fierce competitors have often rolled out identical services and matched each other's prices.

Uber's most recent valuation was $76 billion, and could be worth $120 billion in an IPO. Its listing next year would be the largest in what is expected to be a string of public debuts by highly valued Silicon Valley companies, including apartment-renting company Airbnb and workplace messaging firm Slack.

Uber's debut will be a test of investor tolerance for legal and workplace controversies, which embroiled Uber for most of last year, and on Chief Executive Dara Khosrowshahi's progress in turning around the company. Khosrowshahi took over more just than a year ago.

Uber faces a deadline to go public by Sept. 30, and a filing this week suggests the debut will come earlier than that.

IPOs from Uber and Lyft will test public market investor appetitive for the ride-hailing business, which has proved wildly popular but also unprofitable.

Uber in the third quarter lost $1 billion and is struggling with slowing growth, although its gross bookings, at $12.7 billion, reflect the company's enormous scale.

The Wall Street Journal reported the filing earlier on Friday.