Which country it is?
Payment cards are not a legal tender, so you can do whatever you want, provided you didn't sign a contract not to do.
Payment cards are not a legal tender, so you can do whatever you want, provided you didn't sign a contract not to do.
You can impose a minimum purchase amount for accepting it though.
Certain professions (i.e., taxis) are even forced to accept credit cards.
Are you sure, that it is by law, though? In most countries, it is a contractual obligation: when you make a contract with your bank or payment processor, one of those terms & conditions is not to discriminate against the card payers. The purpose is to force the processing fees on the merchant, otherwise the cards would be at a disadvantage and would not get popular. For a case study, see Southeast Asia (1. cash rules there; 2. you can pay with a card, but you will have to cover the fees too; 3. as a consequence, everyone uses cash, see also point 1).
In the case of taxis, I would understand if they voluntarily had terminals for their own protection (so they would not get mugged for few banknotes), but forcing them... that sounds wrong.
> Are you sure, that it is by law?
It is: Article L112-12 from the Code monétaire et financier. "Le bénéficiaire ne peut appliquer de frais pour l'utilisation d'un instrument de paiement donné." (The seller shouldn't charge any fee for the use of a given payment instrument).
https://www.legifrance.gouv.fr/affichCodeArticle.do;jsession...
More generally, the law requires that the total to pay is to be presented to the client before he choses how to pay.