How much income does TfL estimate it is losing per financial year from passengers travelling on services without paying fares, for example by simply walking through entry and exit barriers without tapping on?

Transport for London (TfL) estimates fare evasion and revenue loss through surveys. However, due to social distancing measures introduced in response to the Covid-19 pandemic, all surveying activity was paused. Consequently, information on revenue loss associated with fare evasion over the last year is not available.