You can file a joint state tax return. You can inherit from each other without state taxes. Differences between civil unions and marriage There are three ways in which civil unions are different than marriages. Partners in a civil union are not affected by federal marriage laws and regulations that touch on marriage. For instance, civil-union partners gain no immigration or citizenship rights for a partner who is not an American citizen, will not collect a dead partner's social security pension, and much more.
Marriage is portable.
That means that if you are married in Ohio, you are married in every other state and country. But no state besides Vermont currently recognizes civil unions. You must not be currently married or civilly unionized to another partner. You must not be too closely related by blood. Both of you must be mentally competent and legally capable of consent.