Passengers will be able to pay for journeys by credit or debit card under rules due to come into force by the end of October.
However, black cab drivers represented by the United Cabbies Group (UCG) are exploring whether this can be challenged in the courts.
It's understood that some cab drivers have taken issue with Transport for London's application of the new rule since it gained overwhelming support in a public consultation last year, including rules on the payments providers which can be used and where the card machine is located within the cab.
It's just the latest development in a renewed row between the cab industries and regulators in the capital.
Uber launched a legal challenge in September, revealed exclusively by City A.M. and won the right to a judicial review of several new rules which will govern its operations in the capital, with the case due to be heard in December.
Black cab drivers last week hailed a victory against the startup, after Mayor of London Sadiq Khan offered support to the trade.
UCG members today voted 83 per cent in favour of postponing the protest which had been due to be held in Central London on Wednesday in light of the mayor's support, which has been slammed by Uber as favouritism.
"Londoners will be astounded at this challenge," said an Uber spokesperson. "Passengers rightly expect to be able to pay by card these days rather than have to stop at a cash machine."