Market Number (MK)

Market Number (MK) is a tracking code used primarily in corporate travel to identify and monitor reservations created through online booking tools (OBTs). 

It is added automatically at the time a reservation is made and stored within the passenger name record (PNR) as a persistent identifier. 

The MK serves as a reference point for tracking fulfillment processes and supporting reporting for corporate travel programs. Once inserted into the PNR, the MK should never be removed, because it functions as a permanent marker that links the booking to a specific corporate channel or workflow.

By tagging each reservation with an MK, travel managers, travel management companies (TMCs), and technology providers can track compliance and monitor booking behavior.