The document outlines the roles of the organisations in the planning system and aims to ensure that timescales are met through better understanding between both organisations and by prioritising processes.
The assembly government is a statutory consultee at both the pre-application and examination stage of the process.
IPC chairman Sir Michael Pitt said: "We look forward to continuing to build upon the constructive relationship we have developed with the assembly government."
Of 51 projects being dealt with by the IPC, the 13 in Wales include an overhead power line, an energy-from-waste plant, a nuclear power station and ten wind farms.
The IPC will be abolished and a major infrastructure planning unit will be established as part of the Planning Inspectorate.
Primary legislation needs to be put in place to achieve these changes and ministers have pledged that there will be a seamless transfer to the new arrangements by April 2012.
The memorandum can be viewed at PlanningResource.co.uk/doc.