It is common place for a surcharge to be imposed on the use of a credit card typically 2 or 3% of a purchase price.
For several years now it has been an offence to charge more to the consumer in surcharges than the traders are themselves charged for processing credit card payments. Also, when the surcharge paid by the consumer is shown to exceed the amount paid by the trader, the difference can be reclaimed by the consumer.
Of course, it is difficult and no-doubt tiresome for consumers to challenge excess surcharges where the information may be difficult to obtain and for amounts that are individually very small.
However, in January 2018 it is likely that no surcharges will be passed on for consumer credit cards usage although there could be still be charges for commercial credit cards.
This is because the new law will result in it becoming so inexpensive for credit card payments to be processed so that traders will be able to absorb the cost themselves rather than pass it on to buyers.
When we know more we will update.

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