Question

At what entity level should the assessment be performed: subsidiary, holding or full group?

The right level depends on who your customer is requesting the rating from, and where your sustainability management is actually governed. An entity-level assessment covers one legal entity and is simpler to manage. A group-level assessment covers all consolidated entities and activates the Coverage indicator, which measures the extent to which sustainability practices are deployed across the group — a real factor for large organisations, simplified for a single-site SME.