Supplier evaluation is the systematic assessment of suppliers against criteria defined in advance, before award to select and afterward to steer ongoing performance.
Terminology. "Supplier rating" and "supplier assessment" are used as synonyms. German practice distinguishes the ongoing, performance-based part as Lieferantenleistungsbewertung.
Two occasions. Before award it is about suitability, capacity, references and price, captured in an evaluation matrix. After award it is about actual performance, steered through supplier performance management.
Criteria. Quantitative criteria (on-time delivery, defect rate, price variance) and qualitative ones (expertise, collaboration, communication). Weighting and scale are fixed in advance.
Difference from an audit. A supplier audit is a one-off, in-depth check, often on site. Evaluation is continuous.
Credibility. Same criteria for comparable suppliers, multiple independent evaluators, documented rationale.