Loss of income and out-of-pocket expenditures are important causes of financial hardship in many patients with cancer, even in high-income countries. The far-reaching consequences extend beyond the patients themselves to their relatives, including caregivers and dependents. European research to date has been limited and is hampered by the absence of a coherent theoretical framework and by heterogeneous methods and terminology. To address these shortages, a task force initiated by the Organisation of European Cancer Institutes (OECI) produced 25 recommendations, including a comprehensive definition of socioeconomic impact from the perspective of patients and their relatives, a conceptual framework, and a consistent taxonomy linked to the framework.