Drivers on GrabHitch, Grab's carpooling service, will need to pay a 10 per cent "platform fee" for all their rides from Friday.
In an e-mail yesterday to drivers, Grab said: "We are now ready for our next wave of development, one that has to be sustainable at its core.
"Your contribution helps us to fund our operating expenses and invest in various initiatives and product enhancements with a sole objective - to channel value back to you in greater fold."
Grab's website said the platform fee, set at a flat rate of 10 per cent of the original fare amount, is required for the "sustainability and improvement" of its service.
This includes ensuring better matches, reducing last-minute cancellations and no-shows from riders, it said.
Private car owners are paid a distance-based fare with GrabHitch. Unlike GrabCar and GrabTaxi drivers, who pay up to 20 per cent in commission, those who use GrabHitch currently earn the full fare for rides.
Previous reports have put the number of GrabHitch drivers at more than 50,000.
The new fee will be deducted from driver's wallets - where payment is collected - within one to two working days. Incentives and bonuses will not be subject to the fee.
Drivers will also now receive a weekly e-statement every Thursday, where they can view their activity and earnings for the previous week.
But those who have negative balances in their driver wallets will have limited access to booking requests, and will have to complete rides to bring their balance back to a positive value to regain full access, Grab said on its website.
GrabHitch, which was launched in November 2015, allows anyone with a valid driving licence to pick up passengers at his convenience. It matches drivers with people who are travelling along the same route.