Employee and Employer Contributions
401(k) plans have two primary sources of funding: the participant’s own salary deferrals and matching or discretionary contributions from the employer. In a divorce, both types of contributions are subject to division, but only to the extent that they were made during the marriage.
Employer contributions may be subject to a vesting schedule. If a spouse hasn’t vested in the matching funds—meaning they’re not fully entitled to that money—those unvested amounts may not be divisible.

