Several commitments to reform fossil fuel subsidies have been adopted in recent years including Sustainable Development Goal 12 (SDG12) which sets a target to rationalize inefficient fossil fuel subsidies that encourage wasteful consumption. Understanding the size of existing fossil fuel subsidies is an important starting point towards achieving this target. However, until recently there has been no commonly agreed approach on how to measure fossil fuel subsidies. UN Environment is responsible for monitoring countries progress under the SDG12 target and has been working with country partners, international organisations and NGOs to develop a robust methodology to measure fossil fuel subsidies. In September, this approach was approved by the Inter-Agency Expert Group on SDG Indicators (IAEG-SDGs) and provides the first internationally agreed approach to measuring fossil fuel subsidies. Based on this approach, UN Environment will start collecting data on fossil fuel subsidies from 193 UN member countries starting in 2020 and will engage with partners to provide further guidance to countries to facilitate their reporting. This process will help improve transparency on fossil fuel subsidies and could provide an impetus to global efforts to reform inefficient fossil fuel subsidies.