New research carried out for the Irish League of Credit Unions (ILCU) has found 66% of users were unaware of their credit card interest rates.
Of those that were aware that interest was charged, nearly a quarter believed they paid a rate of 5% or less and one third said the rate was between 18% and 24%.
In the Irish market at the moment, credit card interest rates range from around 14% to nearly 27%, according to the Competition and Consumer Protection Commission.
The ILCU national survey showed the majority of purchases with credit cards were ad-hoc monthly purchases and 12% used credit cards to pay for future planned holidays.
65% of respondents said they would use their income to clear the balance each month.
Another 18% said they would make only the minimum payment, while 9% said they were frequently unable to cover the minimum charge.
Commenting on the findings, ILCU Head of Communications Paul Bailey said: "The results of this year's survey are worrying, especially amid the cost-of-living crisis that we are currently going through"
"The fact that more than half of those surveyed don't have a true understanding of how credit cards work is a concern, particularly given the number of people who use their credit cards for monthly ad-hoc purchases," he said.
"Credit card companies have a duty to make sure that their customers understand the product they are offering. I would encourage all members of the public to visit the Competition and Consumer Protection Commission website before applying for a credit card, and make sure that they are aware of the charges associated with a credit card account."
The national study was commissioned by the ILCU and carried out by independent research company, iReach Insights, in December 2022.
1,000 adults responded to the online survey.