It looks like the tipping/add fee function on popular cab software Didi Dache is gone. No longer is there a functionality on the popular smartphone app that lets you add tips in increments of 10rmb to assure priority service. Our guess is that this is most likely just an act of lip service. There is always a loophole. You can still use the voice messaging function to just tell the driver you're willing to tip. Or, if you're able to type in Chinese, you can hit the 消话 and type the amount your willing to pay (e.g. "加10快"). Either way, it's highly unlikely your cabbie will turn down the offer of a little extra cash. In related news, Didi Dache also added a new "Zhuan Che" service to the app a few months ago to compete with Uber. I've used this to take an A6 to work a few times, for double the regular fare.