How Do Marriages, Unions and Domestic Partnerships Differ?

Civil unions permit gay couples to declare themselves as each other's reciprocal beneficiaries, which provides them the equivalent of a spouse's rights to hospital and nursing home visitation. (Image credit: follmann |

The ongoing debate playing out in California courtrooms over the validity of Proposition 8, the voter-approved ban on same-sex marriage, has sparked debate over how marriage is defined. In the United States, there are several types of legally recognized monogamous relationships, with some granting couples – gay or straight – more rights than others.

Civil union

Civil unions, also known as registered partnerships and civil partnerships, were first offered in the United States by the state of Vermont in 2000, according to the U.S. Office of Legislative research. In 1994, Vermont had become the first state to extend health benefits to domestic partners. Civil unions are now also recognized by Connecticut, New Jersey and New Hampshire.

Civil unions permit gay couples to declare themselves as each other's "reciprocal beneficiaries," which provides them the equivalent of a spouse's rights to hospital and nursing home visitation. Other civil union benefits can include the ability to access their partner's medical information and to make some personal decisions on each other's behalf.

However, civil unions differ from marriages in that they aren't recognized by the federal government, and under the Defense of Marriage Act of 1996 (DOMA), other U.S. states aren't obligated to acknowledge them either. DOMA defines marriage as "a union between one man and one woman," under federal law, according to the U.S. House of Representatives. So while civil unions offer some of the same rights and responsibilities as marriage, they vary from state to state and apply only on a state level.

Insurance law varies from state to state as well. For example, New Jersey insurance companies are required to offer civil union couples the same policies and contracts they offer to married couples, except where prohibited by federal law, according to the state's Treasury Department.

As for federal income taxes, "single" and "head of household" are the only filing status options for civil union partners. Each partner in a civil union must file a return with the IRS as though they are single.

If the relationship ends, the couple may need to file paperwork with the state to have their legal ties severed. For example, in Vermont, a civil union dissolution form must be completed.

Common law marriage

A common law marriage is the union of a couple that has not had a legally recognized marriage ceremony performed, or has not obtained a marriage license, according to the Internal Revenue Service (IRS). A handful of states recognize common law marriage between a man and a woman. Iowa is the only state that currently recognizes same-sex common-law marriages.

The most common reasons for asking a court to recognize a common law marriage are to deal with issues that arise when the relationship ends, such as property division, establishing child custody, or to establish survivor benefits or other welfare benefits if one of the parties has died, according to the State of Utah Judicial Council.

Common law marriage can only be attained in the District of Columbia and nine U.S. states (Alabama, Colorado, Iowa, Kansas, Montana, Oklahoma, Rhode Island, South Carolina and Texas), according to the U.S. Social Security Administration (SSA). Some states, including Alaska, Florida and Georgia, previously recognized common law marriages and still recognize those that were entered into before the state stopped acknowledging them, according to the SSA.

All states, however, recognize common law marriages that were validly contracted in another state, and the IRS recognizes common law marriages (between straight couples) as valid.

Domestic Partnership

A domestic partnership consists of "two adults who have chosen to share one another's lives in an intimate and committed relationship of mutual caring," according to California Family Code section 297. As such, domestic partners in California are afforded the same rights (such as California tax benefits) and responsibilities that are available to married individuals, according to the State of California Franchise Tax Board (FTB).

In some states where domestic partnership is available, including Wisconsin and New Jersey, same sex couples must formally register with the state in order to be eligible for any benefits that the state may offer. Some states, like Nevada, Maine and Colorado, offer domestic partnerships to both same-sex and opposite-sex couples, according to the State of Connecticut General Assembly.

The benefits of a domestic partnership vary from state to state. For example, California taxpayers that are same-sex domestic partners are eligible to receive an exclusion from their gross income for employer-provided accident and health insurance, according to the California FTB.

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This article was provided by Life's Little Mysteries, a sister site to LiveScience.

Remy Melina was a staff writer for Live Science from 2010 to 2012. She holds a bachelor’s degree in Communication from Hofstra University where she graduated with honors.