1. Employee vs. Employer Contributions
Most 401(k) plans include both employee contributions (deducted from paychecks) and employer matching contributions. In a divorce, employee contributions are usually counted from the date of marriage through the date of separation or division.
The tricky part is the employer contributions. These may be subject to a vesting schedule, meaning your spouse might not have earned them all yet. If employer contributions are partially unvested, the QDRO should clearly state whether only the vested portion is divided or if division includes future vesting (not always allowed).

