A material certificate is what turns a claim about a part's material into evidence. Not all certificates are equal, and knowing the difference prevents an audit surprise.
For precision and regulated components, EN 10204 3.1 is the usual requirement: it gives the chemical composition and mechanical properties of the material with traceability to the heat, signed off independently of production. It is what lets you demonstrate, months later, what a part was actually made from.
A certificate describes the material as it was supplied. On critical batches we also verify the grade in-house by spectrometer, so the material on the machine is confirmed rather than assumed. The two together — certificate and verification — give the strongest position in an audit or an investigation.
State the certificate type (typically 3.1), whether you need in-house verification, and the traceability level your quality system requires. Agreeing this at order entry is what makes it possible — certificates and measurements cannot be retro-fitted to parts already shipped.