Taxis in Paris accept credit cards; I assume Nice is the same. Taxis are required to post a sign, visible from outside of the taxi, if for any reason they are unable to accept a card for payment. Thatīs the rule anyway, the practice may be different.

In a practical sense, I would simply ask before I got into any cab if my only means of payment were by credit card. If you are unsure about communicating, before getting in a taxi, you could simply display your card and the driver should understand you are paying with it.

A friend was recently charged 80€ by a taxi driver on a trip from CDG to the Left Bank. In case you are not yet familiar with recent changes (as he wasnīt), taxi fares from CDG, and from ORY, into Paris are now fixed at 50€/55 and 35€/30€ respectively for the Right/Left Bank.