The requirement to touch in a contactless, Oyster or concessionary card when boarding will initially be required on 85 routes served by single-door and New Routemaster buses.
It will be rolled out across all buses “once further safety measures have been introduced to protect bus drivers”.
Passengers have not needed to present their payment card since April 20 in a bid to reduce the chance of drivers being infected by coronavirus.
But the Government is requiring TfL to resume the collection of bus fares as part of the £1.6 billion bail out agreed last week.
The temporary dropping of fares came as middle-door only boarding was introduced to protect drivers and keep passengers safe from the coronavirus.
It was implemented after 15 bus workers in the capital died after testing positive to Covid-19.