Demonstrations will take place around the US today to highlight the fact that gay married couples must list themselves as ‘single’ on federal tax returns.

Although several states allow gay couples to marry, the United States does not recognise gay marriages at a federal level and so prevents couples from tax benefits straight couples receive.

Marriage Equality USA said its local chapters will make a public point on the federal tax return deadline today that gay couples face a moral and financial disadvantage over straight couples.

Further, the group says the US government is forcing some married couples to lie about their status on the forms.

Thom Watson of Marriage Equality USA said: “It’s that crazy time of year again when the IRS requires you to affirm under penalty of law that you have been completely truthful on your tax forms, while simultaneously the Defense of Marriage Act actually mandates that some US couples lie on their tax forms.

“The federal government requires us to check off the ‘Single’ box on our 1040s, and to file as single, even when we’re not. Our government forces us to lie, and charges us more for the privilege.”

This month, a federal appeals court in Boston began hearing arguments for the repeal of the Defense of Marriage Act (DOMA), the law which states the US’ government will not recognise gay marriages at the federal level.

Adding to several pending legal challenges, another case was lodged this month by the Immigration Equality group in New York, which said the law violates the US constitution’s equal protection clauses by giving gay couples the same rights as straight couples in immigration cases.

The Department of Justice had announced in February of last year that it considered DOMA unconstitutional and would no longer defend it. The Republican-controlled House of Representative’s Speaker John Boehner convened the Bipartisan Legal Advisory Group which is now defending the legislation in the Department of Justice’s place.

California resident Ellen Pontac, protesting the law’s tax implications today with her wife, said: “Same-sex Registered Domestic Partners and same-sex married couples in California are required to fill out a total of four income tax forms when different sex married couples need to fill out only two – making tax time doubly cruel for same-sex couples.”

The more complicated procedure has further cost implications, Thom Watson added: “Because of the additional requirements and complexity, most same-sex couples are forced by the government to spend more money and time to do their taxes than similarly situated opposite-sex couples.”

Stuart Gaffney, Marriage Equality USA Media Director said: “We are encouraged by the recent successful legal challenges of the so called Defense of Marriage Act (DOMA) in federal courts. But until America fulfills its promise of equal justice under the law, tax day will continue to be an annual day of reckoning for how our couples and families face institutionalized discrimination – and are often forced to pay more than their fellow citizens to the same government that denies us equal rights.”

The city of Cambridge in Massachusetts said last year it would pay its married gay public sector workers enough to compensate them for the tax inequity.

Gay spouses on employer-provided health insurance were paying $1,500-3,000 more each year because of federal taxes on health insurance. Straight married couples were not liable to the tax.