Uber lost more than $2.2bn (£1.8bn) in the first nine months of 2016 despite surging revenues, according to reports.
While the San Francisco-based group has seen its value jump to $65bn it is said to have haemorrhaged another $800m in the third quarter and is now on track to lose more than $3bn in 2016. That number does not include further losses made on its now-defunct Chinese operation.
Uber has been hit by a price war with rival Lyft in America and has also spent heavily on ambitious growth plans.
As a private company, Uber does not release full financials, but internal information leaked to Bloomberg shows that the huge losses come despite revenues rising to $3.8bn in the last nine months and set to reach more than $5.5bn for the full year.
Even in the US, Uber's home market, the company lost $100m in the second quarter. Lyft, which is Uber's largest US competitor, has promised investors that it will keep its losses below $150m a quarter.
Bookings - the total fares paid by passengers - reportedly rose to $5.4bn in the third quarter, up from $5bn in the previous three months and $3.8bn in the first quarter. Uber takes commission out of those bookings.
After paying its drivers it is understood to have hit revenues of $1.7bn in the three months to the end of September, up more than half from $1.1bn in the previous quarter.
The group has ramped up spending on new technology and other initiatives, including its controversial self-driving car service and Uber Eats food delivery.
The news comes as Uber said it had discovered safety concerns in its autonomous vehicles, which have trouble crossing cycle lanes.
