Employee vs. Employer Contributions
In a 401(k) plan, contributions are made by both the employee and sometimes the employer. Employee contributions are always 100% vested (meaning they fully belong to the employee), but employer contributions may have a vesting schedule.
It is critical that your QDRO clearly distinguishes between vested and unvested employer contributions as of the date of marital separation or the date used in your divorce judgment. Anything that isn’t vested at that point may not be divisible, depending on the plan rules and the court’s decision.

