This toolkit is designed to help the national greenhouse gas (GHG) inventory coordination team (i.e., National GHG Inventory Coordinator (NIC) and key inventory team members) develop and advance their country’s national GHG inventory management system. Establishing a system to compile and improve the national GHG inventory may seem difficult and complex; however, it does not need to be. This toolkit aims to make the process easier and clearer. It is an iterative and learning-by-doing process. When the inventory compilers maximize the use of supporting resources, each new inventory will build on and improve in quality from previous inventories.