Numerous service providers propose calibration services. How can I be sure that my service provider delivers traceability that is acceptable to my customers and the authorities?

The best solution consists in working with accredited calibration laboratories. If the laboratory is not accredited, then you must make sure that your service provider is competent and establishes traceability with valid references. ISO/IEC 17025 offers guidance on the points to be checked with your service provider. A method is also described in the CFM document "La métrologie un outil pour la qualité" (Metrology: a tool for quality).