Two-thirds of US employers are in need of clarification and guidance on the impact of a Supreme Court ruling on the Defense of Marriage Act (DOMA) from earlier this year, a new study has found.

The survey, conducted by the International Foundation of Employee Benefit Plans, asked employers following the Supreme Court ruling which struck down a key part of DOMA, potentially opening up 1,100 employee benefits to same-sex couples married in states which legally recognise equal marriage.

The foundation’s research director Julie Stitch said: “The decision impacts various types of employee benefits and retirement plans, and poses tax questions for both employers and employees,… Employers have to consider how this ruling affects their health insurance in the midst of implementing Affordable Care Act provisions.”

Over half, 55% of employers operating cross multiple states already offer some benefits to same-sex spouses and domestic partners, the study also found. Such employers operating over multiple states, now provide the same benefits to same-sex couples in states which do not legally recognise same-sex marriage.

Around a quarter of employers asked said they would now extend benefit rights to all married same-sex couples, irrespective of whether their home state legally recognises the marriage.

Almost 16% of employers already extend benefits to all couples, and 40.2% are actually waiting for regulatory or legal guidance.

The survey also found that more employers than ever are offering benefits to unmarried couples, with over 40% of organisations providing benefits to unmarried opposite-sex domestic partners, and another 10.5% saying they were considering adding benefits for such couples.

5.1%, however, said they were considering dropping benefits for unmarried opposite-sex couples.

The largest retailer in the US, Walmart, this week announced that it is to offer health insurance benefits to same-sex domestic partners, as well as opposite-sex domestic partners beginning next year. Its intention is to have a consistent policy for all employees.