Income is considered a community asset and therefore any retirement is also considered a community asset. When you get married all your sole and separate property remains so unless you have co-mingled your assets. In the case of a retirement account, you cannot typically stop an IRA or 401k and start a new account so those funds are almost always co-mingled. Thus, you need to determine the fund value at the time of marriage (typically the number of shares) and the value on the date of filing and/or service to determine the community interest. Generally, the community is only entitled to the share earned during the marriage.