This chapter outlines the necessary steps and information required to implement change of duty in a pipeline system. The function of a pipeline may change at any time throughout its lifetime to allow transportation of alternative fluids. Any change to the fluid conveyed will need a reassessment of the pipeline design to ensure that it is capable of conveying the fluid safely. The chapter shows the recommended practices: Major modifications/remedial work to the pipeline, changes in fluid composition or type, changes in production rates and changes in safe operating limits . A review should be made to determine how the change of duty will affect the originally established corrosion management programme. This will normally follow in-house management of change procedures. The conclusions and recommendations arising from the change of duty review should be used to update and revise the pipeline corrosion management programme and targets.