ATOC wants an agency to support the railcard brands Young Persons Railcard, Senior Railcard and Family and Friends Railcard.
The representative body of the UK's major train operators currently works with ZenithOptimedia for media planning and buying.
A tender was issued to agencies last month, and the deadline for submissions is 13 November.
It is understood that the majority of ATOC's media budget is allocated to digital, with a focus on driving online sales.
In October 2010, ATOC appointed WCRS to develop an advertising campaign for the railcards.
ATOC represents train operators such as First Great Western, Virgin Trains and Southwest Trains.Follow @nickbatten2