'No other way to pay': The sneaky add-on making your bills worse

"The tickets were $100 and there was no other way to pay but online," she said.

Ms Jonasson said the fee wasn't a one-off. It's something she has increasingly noticed as she buys more and more items with her credit card.

"The fees are all mounting up," she said.

"People need to understand the importance of cash purchases and the implications of digital payments only."

Reserve Bank of Australia data shows Australians are losing nearly $1 billion a year in surcharges.

RMIT associate professor of finance Angel Zhong told ACM we are seeing an increase in the "frequency" of card surcharges.

Prof Zhong said the average surcharge was 50 cents with cards now being used for smaller and smaller purchases.

To avoid surcharges she advises people to "carry cash" and prioritise debit cards over credit cards which in in general attract lower surcharges.

The simple answer is yes, surcharges are legal, but within reason.

When you make a purchase using your card, the business you're buying from incurs costs to process that transaction from the banks.

While many larger businesses absorb the cost, many smaller and medium businesses choose to pass the fees on to customers.

The RBA calculates an eftpos transaction costs an average of 30 cents for a $100 purchase to process, or 0.3 per cent, while Visa and Mastercard debit transactions cost 0.5 per cent. Mastercard and Visa credit card transactions cost 0.9 per cent, while American Express card transactions cost around 1.3 per cent.

Businesses are allowed to charge a surcharge but according to the ACCC it must not be more than what it costs the business to use that payment type.

If a business charges a payment surcharge, it must be able to prove the costs it is based on.

If there is no way for a consumer to pay without paying a surcharge, the business must include the surcharge in the displayed price.

Business NSW regional manager Kellon Beard said small businesses in this economic climate were struggling to survive and were left with no choice but to pass surcharges onto consumers.

"The costs of insurance, energy and interest rates are out of control and have collectively eroded what would have previously been healthy profit margins," he said.

Mr Beard said while small businesses knew how "sensitive" prices were for consumers businesses were struggling to stay afloat.

"They need to generate enough business to survive," he said. "In the overwhelming majority of cases, SMEs have to pass these surcharges on."

The RBA's Consumer Payments Survey found consumers paid a surcharge on 7 per cent of transactions in 2022, up from 4 per cent in 2019.

A separate report from payment provider Tyro found hospitality venues to be the biggest adopters of surcharges, with 43 per cent of pubs and bars and 42 per cent of cafes and restaurants adding a fee to card payments in May last year.