Almost €2 million worth of Dublin Bus refund tickets went unclaimed last year, the company has said.
A further €1.5 million receipts remain unclaimed this year.
Dublin Bus gives out refund tickets totalling approximately €1.9 million each year, of which just 25 per cent are claimed, according to spokeswoman.
The company follows an "exact fare no change" policy on all buses for passengers who pay cash fares, to minimise the risk of staff being robbed.
In the case of overpayment, "change tickets" are issued. These can only be exchanged for cash at the company's head office on O'Connell Street in the city centre.
“The auto-fare scheme was introduced in 1999 so that drivers would have no interaction with money. They were being assaulted and robbed as a result of handling cash,” the spokeswoman said.
“We give some of the money from unclaimed receipts to charity, we keep some in a rolling fund and some goes towards maintaining services,” she said.
The company’s spokeswoman said the refund ticket fund could not be donated entirely to charity because it does not belong to the company.
“There is no time limit on when people can claim, so we have to keep a large rolling fund,” she added.
She said Dublin Bus is the only bus company in Europe to offer passengers full refund receipts.
Under its community support programme, Dublin Bus donates approximately €100,000 from the fund to local charities every year. This is considerably less than the amount given to charities five years ago, when the company pulled in €1 million in unclaimed receipts. In 2005, the company donated €250,000 of the unclaimed change to the community support programme.