The transport watchdog has received over 200 complaints about taxis not accepting card payments, or not having a card payment machine.
The complaints, released under the Freedom of Information Act, were made in the space of five months.
Since last September, every taxi in Ireland must accept credit and debit card payments, as well as cash.
By the end of last month, the National Transport Authority had received 229 complaints relating to this new law.
Jim Waldron, from the National Private Hire and Taxi Association, said drivers are adapting to the new regulations.
"I think there are bound to be some problems in the transition period," he told Newstalk radio. "I don't think 229 complaints ... is that much to be honest".
In one complaint, a driver refused to accept a card payment because he said he did not have a machine.
He was asked if he would accept Revolut instead, but he declined and said he would only accept cash.
The NTA issued the driver with a fine.
In another case, a driver refused to take a card payment and when the passenger explained to him it was mandatory, he told the passenger to take cash out of an ATM. The passenger did not take the journey.
The NTA also issued a fine in this case.
In another case, a driver insisted he would have to charge commission on a card transaction.