Cost estimation for the decommissioning of nuclear facilities can vary considerably in format, content and practice both within and across countries. These differences may have legitimate reasons but make the process of reviewing estimates complicated and the estimates themselves difficult to defend. Hence, the joint initiative of the OECD Nuclear Energy Agency (NEA), the International Atomic Energy Agency (IAEA) and the European Commission (EC) was undertaken to propose a standard itemisation of decommissioning costs either directly for the production of cost estimates or for mapping estimates onto a standard, common structure for purposes of comparison. This report updates the earlier itemisation published in 1999 and takes into account experience accumulated thus far. The revised cost itemisation structure has sought to ensure that all costs within the planned scope of a decommissioning project may be reflected. The report also provides general guidance on developing a decommissioning cost estimate, including detailed advice on using the structure.