All Australian businesses are now banned from slugging customers with excessive surcharges for using EFTPOS and credit cards.

New rules mean businesses can now only charge customers what it actually costs them to process payments for EFTPOS, MasterCard, Visa and American Express cards, including bank fees and terminal costs.

“For example, if a business's cost of acceptance for Visa credit is 1.5 per cent, consumers can only be charged a surcharge of 1.5 per cent on payments made using a Visa credit card,” ACCC deputy chairman Michael Schaper said.

“Our message to business is that you are not allowed to add on any of your own internal costs when calculating what surcharge you will charge customers.

“The only costs businesses can include are external costs charged to you by your financial provider.”

If a business wants to set a single, flat surcharge across multiple payment methods, it must be set at the level of the lowest cost method.

“Our advice for businesses wanting to set a single surcharge regardless of the type of card their customers use, is it must be the lowest of all the payment methods,” Dr Schaper added.

“You can't use an average of all payment methods or you will land yourself in trouble.”

The ACCC and consumer advocates Choice have described it as a big win for consumers.

“If you are getting charged a fee and you think it might be excessive, then obviously the first thing to do is try and talk to the business itself and ask what it's about,” Dr Schaper said.

“If not, you can certainly raise it with the commission and we actually have fairly extensive powers and we can go back to businesses and ask them to validate.”

Payment types not included in the ban include American Express cards issued directly by American Express, BPAY, PayPal, Diners Club cards and cheques