Employee vs. Employer Contributions
Generally, the participant’s elective deferrals (money the employee contributes from their paycheck) are 100% divisible. However, employer-matching contributions may be subject to vesting schedules. If the employee hasn’t met the required years of service, some of the employer-provided funds won’t be “vested” at the time of divorce and may be forfeitable.
Your QDRO should be clear on whether it includes just vested balances or addresses a method for calculating future vesting. It’s best to obtain a plan statement that specifically identifies vested vs. unvested balances.

