Employee and Employer Contributions
Contributions to a 401(k) come from both the employee and possibly the employer. Usually, employee contributions are 100% vested immediately. However, employer contributions often follow a vesting schedule. This means an employee might not be entitled to the full employer match unless certain service requirements are met.
A well-drafted QDRO should clearly state whether the alternate payee receives only vested assets or a portion of all contributions (vested and unvested). Any non-vested amounts may be forfeited if the participant leaves employment before full vesting.

