UK supporters of Concern Worldwide who give a fixed contribution to the charity each month had their bank accounts debited by up to 100 times the correct amount earlier this year as a result of computer problems.
The international humanitarian organisation said it moved swiftly to address donor concerns and apologised to them for the mistake.
The UK Charity Commission confirmed it has been in regular contact with the charity since it was contacted over the “serious incident”. A spokesman said it had been monitoring developments in recent weeks to ensure all the steps required to resolve the problems were being taken.
At the end of April, staff at Concern’s UK section made an error processing monthly direct debits of thousands of supporters, leading to increased sums taken from donor accounts.
Refunds were processed in early May after which auditing firm Deloitte was asked by the charity to carry out an independent investigation. It identified two factors which led to the processing issues.
It determined there had been problems with the installation of banking software used in direct debit collections which had led to the amounts due to be collected being increased by a factor of 100. It also found sufficient testing had not been carried out on the new software.
The auditors made a series of recommendations to Concern designed to prevent recurrences of this or similar incidents and to strengthen systems.
“We have accepted them in full and they are now in place,” a spokeswoman for the charity said.