Britons reported overpaying most frequently when tapping their cards, according to survey by service provider Paymentsense.
A third of people admitted to sometimes or never check the amount entered before paying on contactless – and often only noticed incorrect payment when later looking at bank accounts.
But as people often don’t get receipts from the payments, many could find it hard to match bank statements with the transactions, meaning many could overpay without realising, warned Paymentsense.
Only four in ten people believe in keeping a record of payments made by contactless, found the survey.
Britons are more likely to feel they need to keep receipts more for credit card and cash payments.
The survey showed consumers thought they were least likely to pay the wrong amount when using cash.
Guy Moreve from PaymentSense said: “During busy times, it’s easy for any business owner to enter the wrong amount on the card machine and end up accidentally over or undercharging a customer.
“We always advise business owners to enter amounts carefully on their card machine and provide customers with a receipt so they can check the amount themselves and avoid the hassle and cost of issuing a refund or leaving customers short-changed.”