GHG emissions can be accounted to cities in different ways. At present, there are three accounting methods in common use: Territorial-based, production-based, and consumption-based (Barrett et al. in Climate Policy 13(4):451–470, 2013). According to the C40 study (2017), cities could achieve significant emissions reduction by 2030 and build knowledge and foundational capabilities needed to reach net zero carbon by 2050. This chapter will discuss a review of GHG accounting reports and papers. It also describes recent trends and concerns in the accounting process.