You are free to tip and drivers are free to accept.
You can tip your driver at the end of your trip through the app. When prompted to provide a rating, first select a rating for your driver and then you will be given the option to add a tip as well.
You may also tip on a past trip through the app, on riders.uber.com, and from your emailed trip receipt.
To tip on a past trip from the app or riders.uber.com, select the trip from your trip history, and click Add a tip.
From your trip emailed to you, click Add a tip.
Finally, you may also see the option to tip your driver while you’re on a trip. You’ll be able to edit the amount of the tip at any point throughout the trip.
After a trip has ended, you have 30 days to add a tip in the app, on riders.uber.com, and from your emailed trip receipt. You can also give cash to your driver instead.
Note: On Split Fare trips, only the rider who originally requested the trip will be able to select the tip amount for a trip. If a tip is added by the original requester, it will not be split with the other passengers.
Uber takes zero service fees on tips.