The company which runs the public transport smart card scheme is making millions of euros from cards which have expired, the AD says on Friday.

The cards expire after five years and users have to pay €7.50 to buy a new one. In addition, people with anonymous cards have to send back the old card and provide bank account information to reclaim any money left on the card.

Although an estimated €20m has gone unclaimed so far, Translink told the AD it has no idea how many people have not asked for their cash back or what has actually happened to the money.

That will not be apparent until 2016, a spokeswoman told the paper. The money will be spent on passenger services ‘as usual’, the spokeswoman said.

This year and next most of the 6.7 million ov-chipkaart cards currently in circulation will expire. Emptying the card by travelling is difficult because users need to start a bus journey with at least €4 on the card. Train travel requires a ‘deposit’ of €20.

TransLink, which operate the ov-chipkaart system, says the cards have to be renewed every five years because they can become porous and break. In addition, the security technology embedded in the card needs updating.

Passenger lobby group Rover is calling on Translink to come up with a better system for returning travellers’ cash.