We recently finished a trip to Paris and had a wonderful experience with the exception of one cab ride. We had reached our destination at the Eiffel Tower and I handed the driver my credit card and he informed us that he accepted cash only. My wife and I started to panic because the fare was 35 Euros and we had about 30 Euros and some change. Not sure what to do I realized that I also had a US ten dollar bill and added that to the pile of cash. He accepted this and we were on our way.
I mentioned this to our clerk at the hotel and he informed us that by law all taxi drivers must accept credit cards! He said I should of told him that if he didn't accept our card than he would not get paid and we would be happy to talk to a police officer about it. We think the driver was insisting to take cash in order to keep it off the books. Also, we did not ask for a receipt which was another mistake.
Fortunately I figured with the additional US money we only overpaid by about 5 dollars but wanted others to be aware of our experience so you wont be a naive as we were!