Local authorities (regions, departments, metropolitan areas and towns) are increasingly involved in defining and implementing policies to combat climate change. This is not a simple task, as beyond emissions generated by their administrative services, most greenhouse gas (GHG) emissions in their territorial jurisdiction are beyond their direct control. Often given responsibility for the emissions of all actors within their administrative boundaries, different local authorities are often restricted in their ability to foster reductions through their attributed jurisdictional competencies. Faced with such limitations in fostering reductions, voluntary offsetting is one of the tools available to local authorities for reducing territorial emissions, by either purchasing carbon credits in order to offset emissions or by selling generating credits in order to create a source of financial income. Although the voluntary offset market is still small in comparison with the compliance market created by the Kyoto Protocol, market participants find it to be a more flexible, innovative and responsive framework. In exchange, average prices, which are determined on an over-the-counter basis, are usually lower than those for compliance credits. At the same time, the compliance and voluntary markets reveal very significant differences linked to the nature of the project. This Climate Report presents ten case studies in order to better understand how and why local authorities use this instrument. Analysing the offer, local authorities that sell carbon credits account for a very small percentage – just 3% – of voluntary offset projects. Their typical profile is that of a US local authority, which is implementing a methane elimination project at its waste disposal site, primarily in order to anticipate future regulation and to obtain a source of additional financing. Local authorities’ share of the demand for voluntary credits is harder to quantify. The case studies nonetheless shed some light on the determining factor for a successful offset programme: namely a carefully designed project rooted in the local authority specific context and is shared by local players. In fact, the vast majority of local authorities prefer to buy carbon credits generated by projects implemented within their jurisdiction, in order to maximise other economic, social and environmental benefits than the simple reduction of GHG emissions. The choice of the financing vehicle (dedicated framework, tender or tax) depends on the size of the offset programme and on the type of projects targeted. It has no determining impact on the success and sustainability of the offset programme.