Employee and Employer Contributions
One of the most important features of a 401(k) plan is that it consists of both employee and employer contributions. In a divorce, only vested employer contributions are divisible through a QDRO. If the participant (your spouse) is not fully vested, the alternate payee may lose access to a portion of the total balance. The QDRO needs to be clear about whether the split covers all vested balances only or includes provisions for future vesting.

