Thousands of customers are seeing payments rejected despite having sufficient funds in their accounts.
As a result, many shoppers are left red-faced due to little or no knowledge about new anti-fraud rules for contactless payments.
Last year people were told failure to input their Personal Identification Number (PIN) after every five contactless transactions would see the payment rejected.
The rules also mean people must enter their PIN each time they make a single transaction above £42 or consecutive contactless payments totalling £127.
CEO of leading payment solutions company myPOS, Christo Georgiev, said many British shoppers have no idea about the new rules.
He said: "Retailers are expected to comply with the new Strong Customer Authentication (SCA) rules before March 2021, but some are enforcing them early and shoppers are being caught out as a result.
Customers who have fallen foul to this are often left embarrassed but the CEO says its not all doom and gloom, it just means the card has reached the limit of successive contactless payments.
“When this happens, there is no need to panic, shoppers should just insert their card in the machine and input their PIN and the transaction will go through," he said.
With an estimated 112 million contactless cards in the United Kingdom, contactless payment systems such as bank cards or mobile phones now account for one in three payments in the United Kingdom.
Many customers find them faster and more convenient than alternative payment methods such as cash or Chip and PIN.
But the ease of use makes it vulnerable to fraud.
Mr Georgiev said the company has notified merchants and retailers across the European Economic Area and they make shoppers fully aware of the new rules to prevent "unnecessary disruption."
