The certification materials issued by the unit must meet the following three conditions at the same time in order to have evidence effect:

1, stamped with the official seal of the company;

2. Signature or seal of the legal representative and responsible person of the unit;

3. Signature or seal of the producer of the certification materials.

This is a formal requirement stipulated by law, and only when the certification materials issued by the unit meet the above formal requirements can they have evidential effect.

Legal basis:

The evidence in Article 63 of the Civil Procedure Law of People's Republic of China (PRC) includes: (1) the statement of the parties; (2) Documentary evidence; (3) Physical evidence; (4) Audio-visual materials; (5) Electronic data; (6) Testimony of witnesses; (7) Appraisal opinions; (8) Records of the inquest. Evidence must be verified before it can be used as a basis for ascertaining facts.