Uber Technologies said on Thursday that the ride-hailing services company had completed 5 billion trips, as of May 20.
Uber, which was founded in 2010, said 156 trips started at the same time, helping the company cross the milestone.
Earlier this week, Australia's workplace regulator said it is investigating Uber over the way it recruits drivers, after a drivers group sought employee rather than subcontractor status.
The Fair Work Ombudsman plans to focus on whether the San Francisco-based startup, which makes apps that allow people to book journeys on their smartphones, is in breach of Australian workplace rules, a spokesman said.
"We have started an investigation," the spokesman said. "That is all that can be said at this time."
The ombudsman is empowered to take legal action to force firms to comply with workplace laws and pay employees minimum wage and retirement benefits.
Uber defended the way it engages drivers, saying it allowed them more independence.
Also this week, Uber said it had won the right to appeal against a court decision in favour of plans by a London regulator to impose new English reading and writing standards in a move which could deprive it of thousands of drivers.
In March, the San Francisco-based firm, which allows people to book journeys on their smartphone, lost a court battle against Transport for London (TfL), the latest setback as the authorities crack down on the ride service.
© Thomson Reuters 2017