This study assesses whether existing international carbon market methodologies for determination of additionality and baselines and monitoring, particularly those from the Clean Development Mechanism (CDM), can be adjusted to transition to the Article 6.4 mechanism. CDM methodologies need to be modified to align with the more rigorous requirements of Article 6.4 of the Paris Agreement. Different options are discussed to operationalise the Article 6.4 methodology requirements. The Focus is on the option to develop overarching methodological tools that can be applied to make CDM methodologies “Article 6.4 proof”. This approach is beeing illustrated by applying it to two CDM methodologies, ACM0005 and ACM0006.