TSE ISO/IEC Guide 28

TSE ISO/IEC Guide 28 provides general guidance for third-party certification systems used for products. It explains the basic structure of a scheme that determines product conformity through initial sample testing, assessment and surveillance of the relevant quality system, and follow-up testing of samples taken from the factory or the open market.

How a third-party product certification scheme is organised

In this model, certification is not based on a single test result alone. Instead, it combines product testing with continuing oversight of how the product is made and controlled. The term third-party means the certification decision is made by an independent body outside the supply chain. In general technical terms, this approach helps link product conformity to ongoing production control, not only to a one-time sample.

Conformity mark and certificate conditions

The Guide also addresses the conditions for using a mark of conformity and for granting a certificate of conformity. These are related but distinct tools: a mark is the visible conformity claim used on the product or its documentation, while a certificate formalises the certification decision. Annex A includes a model checklist of requirements, which offers a structured way to review the essential elements of a third-party certification system.

The document corresponds to system 5 product certification as described in ISO/IEC Guide 67. It is therefore relevant to organisations that work with certification models based on product sampling, quality system surveillance, and continuing conformity control. Although this Guide has been withdrawn, it remains technically useful for understanding how a third-party product certification scheme is built and managed.