Transport for London has opened a public consultation on proposals to remove the option to pay by cash on all bus services in the capital in 2014.
TfL says that cash fares are expected to fall to less than one per cent of total bus journey's this year following the successful roll-out of contactless payment cards (CPC) on London's public transport services last year.
Currently around 23,000 trips per day are made using CPC, with around 1000 new users each day.
TfL says that savings of up to £24m per annum by 2019/20 will be expected due to reductions in the cost of handling cash over the network.
If people don't have enough credit on their pay-as-you-go Oyster card TfL is considering introducing a new feature that will allow passengers to make one more bus journey, helping them get home or to the nearest station or Oyster Ticket Stop. The negative balance on the card would be removed on the next successful top-up.
The consultation process will run until October this year, at which point the transport authority will submit its proposals to the Mayor of London for approval.