TAG, formerly known as The Appointment Group, organises travel itineraries for pop stars including Lady Gaga and Rihanna.
According to Sky News, ECI Partners and Livingbridge are understood to be among the suitors pursuing the company.
The auction, which is being run by bankers at Rothschild, is now in its second round.
TAG was founded by John Gianquitto and Maurice Veronique in 1988 and now employs more than 300 people.
Travel industry insiders told Sky News that the company could be worth around £150m.
Other publicly disclosed clients include Depeche Mode, Foo Fighters and Jay-Z.
TAG has a global presence with offices in Los Angeles, Nashville, Miami, New York, London, Manchester, Melbourne, Hong Kong and Singapore among others.
