When Colorado enacted civil union legislation in March 2013, effective May 1, 2013, Colorado became the third state to provide the status of civil unions to both same-sex couples and different-sex couples, as Hawaii and Illinois had until both of these states allowed same-sex marriage in 2013.
In January 2021, the Colorado Supreme Court made a ruling to retroactively recognise common-law same-sex marriage.
A UCLA study of the impact domestic partnerships for same-sex couples would have on Colorado's budget concluded that allowing same-sex couples to enter into domestic partnerships under the "Colorado Domestic Partnership Benefits and Responsibilities Act" would result in a net gain of approximately $1.2 million each year for the state, resulting from savings on expenditures on state means-tested public benefits programs and from an increase in sales tax revenue from registration celebrations.
Since July 1, 2009, unmarried couples in Colorado have been able to enter a designated beneficiary agreement – similar to reciprocal beneficiary relationships in Hawaii – which grants them limited rights, including making funeral arrangements for each other, receiving death benefits, and inheriting property without a will.
[4] The law, House Bill 1260,[5] was enacted by the legislature and is valid for estate planning, property purchases, medical decisions and certain benefits such as life insurance and retirement-plan disbursements.
[16] Unlike earlier versions of the legislation, it did not include language allowing adoption agencies to withhold their services from a couple in a same-sex civil union.
Following the House vote, Denver's Roman Catholic Archbishop Samuel J. Aquila purported that "The ability for religious-based institutions to provide foster care and adoption services for Colorado's children is now dangerously imperiled".
[23] Governor Hickenlooper signed a bill permitting joint state income tax filing for civil union and out-of-state same-sex married couples.