The Magnetic Cleanliness Handbook, intended to complement and expand the notions contained in EN 16603-20-07 "Electromagnetic compatibility" (equivalent to ECSS-E-ST-20-07C), will constitute a best-practice guide on testing and give recommendations on system-level predictions for engineers of space industry and test centres. The following main areas will be covered: - Survey of available test facilities and employed procedures, - generic best-practice design and test guide with recommendations on tailoring, and - survey of system-level modelling software and recommendations for their utilisation AC magnetic field requirements and their verification have become increasingly important. This domain will also be covered in the handbook. Justification: At the ESA Workshop on Aerospace EMC, 21-23 May 2012, the special topic of Magnetic Cleanliness has received strong attention from industry and academia. More than a complete full day with four presentation sessions and several poster presentations has been dedicated to Magnetic Cleanliness. In intense discussions in the sessions and during breaks, the need for a coordinated approach on Magnetic Cleanliness Programmes for space projects and especially Magnetic Cleanliness measurement and modelling techniques has emerged and has been repeatedly stressed across all participants. A typical small-scale Mobile Coil Facility for unit-level Magnetic Cleanliness testing exists at ESTEC and has been already used for project support to various programmes (e.g. among others Ulysses, Giotto, Cluster, Swarm, LISA Pathfinder, ISS and Galileo) and will be used in the coming years (e.g. Solar Orbiter, Juice). Since several other small- and large-scale test facilities are operated, it is in the interest of the European Space Community to harmonize existing procedures. Moreover, the modelling of magnetic cleanliness at system level has been tried with a variety of approaches that vary widely in terms of effort and accuracy. Recommendations on selection and utilisation of the most economic approach for a given mission objective require a comprehensive technical understanding in the European Space Community.