Employee and Employer Contributions
With 401(k) plans, contributions may come from both the employee and the employer. How each is divided can differ depending on whether the contributions were made during the marriage (marital property) or prior/post-marriage (separate property).
Employer contributions often come with vesting schedules. Unvested amounts at the time of divorce may not be included in the QDRO unless and until they vest. Be aware that if your QDRO tries to assign unvested funds, the plan will likely reject it.

