Planned outages are a major contributor to nuclear power plant (NPP) non-availability, risk and cost. Effective management of planned outages is a key factor for improvement of NPP safety, availability and competitiveness. To support outage management, an outage monitoring system is implemented that follows all the fundamental and critical activities and deadlines in each phase of the outage. The IAEA has produced this publication on indicators for planned outage monitoring to complement a series of technical publications related to practices regarding outage management and cost effective maintenance. The aim of this publication is to provide guidelines for outage monitoring systems, examples of specific outage indicators and good practices in outage monitoring. This publication outlines a set of outage indicators that could be considered by operators of NPPs when establishing or revising their own specific outage indicator systems.