Travellers in London were forced to pay full price fares on Saturday as the computer system for the Oyster travel smartcard encountered technical problems during the morning.
Card readers on the Transport for London (TfL) network weren't working for much of the day as a result of the problem, which occurred between 05.30(BST) and 09.30.
Travellers who were unable to use their cards had to pay the full cash fare for their journeys rather than the discounted Oyster fare but will be automatically refunded from Tuesday.
A TfL spokesman told our sister site silicon.com: "Anyone who received a maximum fare on Saturday will be automatically refunded, they don't have to do anything to do that."
People who used their Oyster cards before the 09.30 outage as well as those who topped up their card at an Oyster ticket shop during the day, may find their cards no longer work. These cards can be replaced free of charge at any London Underground office.
The spokesman said around 65,000 people were affected by this problem but 30,000 have already had their card replaced.
Freedom Pass or Young Persons Oyster card holders affected will have to apply for replacements but will be allowed to continue travelling while these are issued.
The problem has now been rectified and cards are being accepted across the network. Shops selling Oyster tickets were also affected but the majority were brought back into operation during Sunday.
TfL is investigating the cause of the outage with technology partner TranSys and has apologised for the inconvenience caused.
