The Curb app is free to download for iPhone and Android devices. Curb charges standard taxi fares that vary by city. A service fee of $1.95 is added to the fare to help support Curb technology upgrades and service improvements, and an additional fee may be applied to rides that are booked in advance in select markets. You'll be able to choose a tip percentage at the end of your ride. You can also set a default tip percentage to be applied to all of your rides.
If you book a ride in the Curb app and cancel it more than 30 seconds after your driver has been assigned, you may be charged a $3.00 fee to compensate the driver.