Rationally understanding the evolution of the physical world is inherently linked with the idea of causality. It follows that agents based on automated planning have inevitably to deal with causality, especially when considering imputability. However, the many debates around causation in the last decades have shown how complex this notion is and thus, how difficult it is to integrate it with planning. This paper's contribution is to link up two research topics-automated planning and causality-by proposing an actual causation definition suitable for action languages. This definition is a formalisation of Wright's NESS test of causation.