Enterprises should sign a training agreement before employee training, indicating that the training fee needs to be returned in proportion.

If the unit has not signed an agreement, there is no reason to ask the employees to return the training fee, because the unit has the obligation to train the employees.

If there is an agreement, you can directly write:

XXX:

According to the XXXX project training agreement signed on XX, XX, XX. When the employee terminates the labor relationship with the unit, if it fails to meet the requirements of XXX, it is necessary to return the training fee.