Vested vs. Non-Vested Employer Contributions
One of the first issues we review when dividing a plan like the Exceptional Hearts LLC 401(k) Profit Sharing Plan & Trust is whether the plan has a vesting schedule for employer contributions. In many 401(k) profit-sharing arrangements, employer contributions are subject to years-of-service vesting. That means your ex might only be entitled to a portion of the account depending on how long you were employed at the time of divorce.
A QDRO should clearly state that only the vested portion of the employer contributions is to be divided (unless your divorce agreement says otherwise). Any unvested contributions typically revert to the employee if not fully vested by the time of division.

