As part of international agreements, countries must report their greenhouse gas emissions. In associations of states such as the EU, it is desirable that the data used for reporting is also comparable. To date, there have been various methods for collecting data on forest soil, some of which differ so greatly from one another due to historically evolved circumstances that the data obtained cannot be harmonized. In addition, there are countries that have not yet collected any data, as a systematic survey, whether as part of an inventory or long-term monitoring, is time-consuming and cost-intensive. With this guideline, we therefore propose a basis that can be used in future to collect data for greenhouse gas (GHG) reporting in forest soils. The methodology is based on the ICP Forests manual and is limited to the parameters relevant for GHG reporting and their interpretation. It is possible to add individual parameters. With the help of the guideline, forest soil investigations can be linked to existing inventories (e.g. forest inventories) or the existing ICP Forests network can be consolidated with less complex sites.