Some customers using Royal Bank of Scotland cash machines gave donations to charity "in error" when it first implemented ATM giving last autumn.
The bank, which operates about a quarter of the UK’s cash machines, released figures showing that a total of £347,000 had been given to charity and that total donations were 8,051, giving an average donation of just over £43.
Last autumn, Link, the company that provides the network behind most of the UK’s 66,000 cash machines, announced that it had put in place a system that enables people to donate to charity at any of the ATMs attached to the Link system. So far, only the RBS Group has implemented the system at all its Link machines.
Link said the average cash donation from its machines enabled for charitable giving was actually £5 so far. RBS said its relatively high average donation was explained by money "donated in error".
The discrepancy between the two averages suggests that as much as £300,000 could have been given in error. A spokeswoman for the RBS Group said she could neither confirm nor deny this.
"When we first introduced it, there were some instances in which the customer donated to charity in error," she said. "In all cases, we refunded the customer and made sure the charities were not disadvantaged by honouring the original donation.
"We have since introduced further checks on our ATM screens to reduce the likelihood of this error happening again."
The RBS Group is the only major high-street bank chain to introduce the Link scheme; it has also been introduced by the independent ATM provider Bank Machine, which runs 4,000 ATMS in places such as garages and shops. HSBC has run its own separate scheme on its 3,400 ATMs since 2006.
Several other major banks said they had no plans to implement the scheme at present. The Co-operative Bank said that it had not done so partly because customers misunderstood ATM giving.
"Customers are often confused about who is donating – the bank or themselves," a Co-op spokeswoman said.