The position is that where a couple is cohabiting, rather than married or in a civil partnership, they are treated as separate and unconnected individuals for the purposes of income tax. Each partner is a separate entity for tax purposes and, therefore, cohabiting couples cannot file joint assessment tax returns or share their tax credits and tax bands in the same manner as married couples. The basis for the current tax treatment of married couples derives from the Supreme Court decision in Murphy vs. Attorney General (1980), which held that it was contrary to the Constitution for a married couple, both of whom are working, to pay more tax than two single people living together and having the same income.
However, a cohabiting couple where both partners are working get, in total, the same tax credits as a married couple or couple in a civil partnership (i.e. €3,300). In addition, the same amount of income is subject to tax at the 20% rate (i.e. €32,800 each). This equates to the €65,600 threshold in the case of a married couple or couple in a civil partnership.
If both cohabitants earn in excess of the standard rate band (i.e. €32,800), then they both pay tax at 41% on any income in excess of €32,800. Married couples or couples in a civil partnership where both individuals work get the same treatment.
The difference between the two groups in relation to income tax is the ability of married couples or civil partners to transfer certain tax credits such as the personal/married credits and part of the tax bands, i.e. the tax band of €65,600 available to married couples or couples in a civil partnership with two incomes in 2013 is transferable between spouses up to a maximum of €41,800. This is of benefit where one of the individuals earns less than the 20% tax threshold of €32,800 or where one of the individuals has no income.
The treatment of cohabiting couples for the purposes of social welfare is primarily a matter for the Minister for Social Protection. However, it is also based on the principle that married couples should not be treated less favourably than cohabiting couples. This was given a constitutional underpinning following the Supreme Court decision in Hyland v Minister for Social Welfare (1989) which ruled that it was unconstitutional for the total income a married couple received in social welfare benefits to be less than the couple would have received if they were unmarried and cohabiting.