Employee vs. Employer Contributions
The participant’s personal contributions to the 401(k) (employee contributions) are fully divisible. But employer contributions can be subject to a vesting schedule. That means the employee may not own 100% of the employer contributions at the time of divorce. In the Sandys Pool Service LLC 401(k) Plan, if your spouse has only worked there a short time, a portion of their employer contributions may be unvested—and you likely can’t receive a share of that unvested portion.
A proper QDRO must state that only vested portions are divided, or clearly define whether the alternate payee (the non-employee spouse) is entitled only to vested amounts as of the date of division or also to any future vesting.

