Zip Oyster cards hold £600,000 'unclaimed'
If your child gets free travel with Zip Oyster cards you may find some unclaimed cash on their travel pass.
At the end of every school year, thousands of school children automatically have their Zip Oyster travelcards cancelled as they move into another age category.
The cards give free travel on buses and trams, but to get child fares on the Tube and trains parents have to load money onto the cards.
They were introduced in part so Transport for London (TfL) and the mayor could take them away from unruly children through a code of behaviour.
TfL says that in 2012, about 20,000 Zip Oyster photo cards were withdrawn.
However, at the end of the year not surprisingly there is quite a lot of money left on them.
The BBC's Freedom of Information (FOI) researcher Laura Francis has found that around £600,000 was unclaimed since 2010.
The amounts left on cards are small - at most £1.53 and as little as 7p - but in total it is a tidy sum for TfL.
Shashi Verma, TfL's Director of Customer Experience, said: "We encourage anyone who has finished with an Oyster card to have their outstanding balance reimbursed.
"Unused pay as you go balance on a Zip Oyster photo card can be reclaimed at any time at any London Underground ticket office or TfL Travel Information Centre, even when the card has expired."