Two gay couples in the US state of Kansas are suing the state which does not allow them to take advantage of the benefits of filing a joint tax return.

The couple filed the lawsuit in the Shawnee County District Court on Monday, reports the Associated Press.

It argues that the Department of Revenue’s policy which bans same-sex couples from filing joint tax returns is discriminatory.

The lawsuit says it violates the couple’s right to equal protection, ad goes on to question whether the department had the authority to set its policy through a notice which was given in October.

It notes that despite the Kansas constitution saying the state cannot recognise same-sex marriages, that the federal Government does.

Michael Nelson and Charles Dedmon of Alba and Roberta and Julia Woodrick of Lawrence, two couples both married in California, filed the lawsuit.

The department has not commented on the issue.

Back in June, the US Supreme Court struck down California’s 2008 ban on same-sex marriages, Proposition 8, allowing marriages to continue almost immediately.

The Supreme Court also struck down a key part of the Defense of Marriage Act, opening up marriage benefits to same-sex couples.