Supplier evaluation is often approached as a scoring problem, while many deployments fail due to lack of harmonization across sites, entities and evolving external constraints. This paper proposes a framework to harmonize supplier evaluation through a minimum common standard and modular extensions. Design/methodology/approach – Conceptual synthesis of recurring implementation challenges in multisite and turbulent contexts. The framework defines a Minimum Common Standard (process, data, evidence, rules, governance), a modular architecture to absorb local variability and new external requirements, and a five-phase rollout model. Three structured vignettes (Create/Extend/Transform) illustrate applicability. Meta-performance indicators and failure modes are proposed. Findings – The framework specifies what must be standardized to ensure comparability, auditability and actionability (and what should remain configurable). It separates internal harmonization (cross-entity comparability) from external harmonization (integration of new standards/regulations/constraints via modules), and provides a phased rollout logic to reduce adoption risk. Originality – The paper reframes supplier evaluation from “how to score suppliers” to “how to harmonize an evaluation system under organizational and external turbulence”, introducing a Minimum Common Standard and modular governance as a deployable blueprint. Keywords – supplier evaluation; harmonization; minimum common standard; modularity; governance; phased implementation. Paper type – Conceptual paper.