At the moment just half of taxis accept payments by plastic but the transport body wants all passengers to have the option of travelling without cash – possibly even using their Oyster card.
It has launched a consultation for passengers and drivers into the proposals but stressed that Londoners would still be able to pay for their journey with cash whatever the outcome.
It comes as TfL announced that train company Bombardier had been awarded a £260 million contract to provide a new fleet of trains for routes out of Liverpool Street that became part of the network last month.
The deal, which will provide 45 air-conditioned trains with walk-through carriages along the old West Anglia routes, will support hundreds of jobs in Derby.
A collapsed signalling contract with Bombardier in 2011 left taxpayers with an estimated £80 million bill, but the firm is now also providing 65 new trains for Crossrail when it opens in 2018.