The option is available only for bank card payments.
If you are happy with your trip, you can give a tip to the driver. To enter the tip amount for all trips, select Menu → Tip and choose the percentage of the trip cost. You can change the tip amount from the app menu or at the end of the trip once you've rated the driver.
A tip is charged automatically if you give a positive rating to the driver within 30 minutes after the end of the trip (or don't give any rate) and tap Done.
If you give a negative rating to the driver within 30 minutes after the end of the trip and tap Done, no tip will be charged.
If you don't tap Done within 30 minutes after the end of the trip, the tip amount will be reserved on your card for 24 hours. You can change the tip amount within this time frame or leave everything as is – in this case, the tip amount entered will be withdrawn within a day.