"Labor Contract Law" allows employers and employees to agree on the service period, mainly giving the unit the right to set up liquidated damages. Without necessary binding force, the service period without liquidated damages is meaningless. However, the law does not mention who should keep the certificate obtained through training.
Generally speaking, the certificate is a proof of personal attributes, and the unit cannot play its value by virtue of the employee's certificate. But in fact, it has played a role in preventing employees from leaving their jobs to a certain extent. I noticed that your company didn't use liquidated damages to prevent the trained employee from leaving, so he must keep the certificate to protect his own interests.
The unit paid the training fee, which shows that the unit has money connection with this certificate. Under the premise of clear agreement between the two parties, from the current law, there is nothing obviously illegal for the unit to keep the employee's documents. What's more, the certificate is only a vocational skills training certificate, not a diploma or other academic certificate, which will not have a significant impact on employees' future employment.
However, after all, certificates have close personal ties with employees. The employee leaves his post before the service expires, the training fee is deducted by the unit, and the financial connection between the unit and this certificate has been cut off. At this point, the unit should return the certificate to the employee and should not keep it. (End)