A London court will consider later today (Monday) if Uber is "fit and proper" to hold an operator licence in the UK capital.
The taxi app company will make its case at Westminster Magistrates' Court in a hearing expected to last several days.
Last September, Transport for London refused to renew Uber's licence on grounds of public safety and security, the BBC reports.
Uber said it has since made significant changes, like improving the procedure for reporting criminal actions.
The court will decide whether Uber is fit to hold an operator licence now as opposed to the point when Transport for London decided not to renew the licence last September for reasons it outlined in a 21-page document.
Uber has been allowed to carry on operating in London while awaiting to appeal.
"I know we got things wrong and that we have more work to do. But I promise Londoners we will keep listening and improving as Uber moves forward in a new direction," Uber's UK general manager, Tom Elvidge, said in May.
Justin Bowden, national secretary at GMB, the union for taxi drivers, said: "Uber lost its licence in London because it refused to play by London's rules, particularly on the crucial issue of passenger safety, and it won't get it back until it accepts that an 'Uber's way, or no way' attitude to safety and its drivers will not prevail."
According to the firm, 3.6 million passengers regularly use its app in London and it has 45,000 drivers in the city.
Since being denied a licence to operate in London, Uber has implemented a number of changes.
Uber now reports crimes directly to the police - previously it had logged criminal complains with Transport for London, which caused delays.
Drivers are now only allowed to use the app in the region they hold a private hire licence.
The working hours of its drivers are more tightly regulated.
A licensed driver on its app must take an uninterrupted six-hour break after 10 hours of driving with a passenger or travelling to a pick up.
Drivers who do not take a long enough break will not be able to log in to the app and take trips.
The company has also revamped its leadership. Three independent non-executives have been appointed to its UK board.
