Any production may require manufacturing, processing, treatment of materials and components that are considered external to the production itself. Usually, companies with ISO 9001 certification have specially developed, managed vendor inspection procedures that cover materials along with equipment including spare parts and instruments.

Vendor inspection sample size depends primarily on supplier’s reliability. Full incoming control usually is impractical, there is an explicit selection - one item or a sample taken from one or several batches/lots. A set or controlled parameters also may vary based on incoming volume or quantity.

Usually, three main methods are used:
- Accompanying documentation control
- Visual and measuring testing
- Laboratory tests

Currently various companies establish vendor inspection services on their production sites and warehouses. Yet the conditions of such a control may be much stricter than with core operations.