There will be a visible taxi driver permit somewhere on the dash. Of course can be faked.

I got a yellow taxi many years ago, before I could utter a single Chinese word, the gf negotiated a price, and and  as we got in the driver took the taxi sign off the roof and threw it on the back seat. It was polystyrene .

I use black cars all the time now. 

A few weeks ago I got a black car and it turned out the driver was an off duty copper. 

In China, a taxi is retired after clocking 500,000km and is then sold as a private car. Theoretically these cars can be bought and then illegally returned to working life. Often these taxis have manipulated meters that will charge a lot more than official taxis.

The difficulty of this matter is that these taxis are incredibly hard to recognize. Luckily, there are a variety of measures you can take to avoid being ripped off:

l  Keep track of how fast the meter is going up and if you have a feeling it is going up a lot faster than it usually does, get out and hail a different one.

l  Make sure you aren’t being given fake money. This mainly happens when handing 100 yuan bills to drivers which they then reject – either calling it a fake or saying they have no change.

l  Always carry small change when planning on taking a taxi.

l  Ask the driver if he has change before handing him the bill.

l  Fake cabs are most common around the subway stations, shopping malls, and also near major tourist attractions. The most serious areas are the railway stations and Beijing capital airport.

l  Check to see if the receipt is fake and try to take a photo of the license plate of the car.

All in all, we’re afraid there isn’t much anyone can do. But we suggest you use your common sense. 

when the fare is 4 times what it should be that would be a clue