Employee and Employer Contributions
Most 401(k)s are made up of a mix of employee salary deferrals and employer matching or profit-sharing contributions. Sometimes employers impose a vesting schedule on their contributions. Only vested contributions (those the participant “owns”) can be distributed to an ex-spouse.
Spouses may assume they’re entitled to half of the total plan balance, but that’s not always true if some portion is unvested. This becomes especially important if the divorce occurs close to the vesting “cliff.”

