The due diligence process provided as guidance evaluates suppliers based on their Supplier to Zero (StZ) Certification Level, whether they are new or regular and whether the material is strategically critical. Depending on these factors, input materials may require:

• No testing (e.g., StZ Level 3 suppliers).
• Random testing (e.g., regular suppliers with StZ Level 2 or 1 certification).
• Regular testing (e.g., new suppliers without certification).

This process helps facilities apply proportionate testing based on risk level. Facilities should demonstrate a system of due diligence process for evaluating input materials for restricted substances risk, preferably based on the guidance given in Supplier RtZ. 

The due diligence flow outline in Suppliers RtZ serves as guidance and facilities may adapt or develop their own processes accordingly.