The average merchant card service fee for small businesses is about 1.2 percent to 1.5 percent.

Credit card company Visa is calling for a ban on the surcharge fee some merchants charge card-paying consumers at the point of sale.

The Commerce Commission was undertaking a review of card charges, and considering cutting the regulated interchange fee card companies can charge banks by as much as 75 percent, for example.

Card interchange fees were in turn passed on by banks to merchants at whatever rate the merchant can negotiate, meaning that some pay much more than others.