If you accrued funds into your 401(k) during your marriage, those funds are considered marital property and hence your spouse is entitled to a credit for one-half of them. However, if you had funds in a retirement account prior to your marriage, the amount in the 401(k) at the time of your marriage is considered separate. Practically speaking if you contributed to the same account before marriage and after, you will need a statement from your retirement provider which clearly indicates the amount in the account on the date of your wedding. You would then get a statement showing the date you or your spouse filed a petition for dissolution of Marriage, then subtract the latter from the former. That is the amount that your spouse would be entitled. The retirement provider can separate a spouses share from the original account. BEWARE though that if you remove those funds from a 401(k), you will be taxed on them.