Where a couple is cohabiting, rather than married or in a civil partnership, each partner is treated for the purposes of income tax as a separate and unconnected individual. Because they are treated separately for tax purposes, credits, tax bands and reliefs cannot be transferred from one partner to the other. Cohabitants do not have the same legal rights and obligations as a married couple or couple in a civil partnership which is why they are not accorded similar tax treatment to couples who have a civil status that is recognised in law.
The basis for the current tax treatment of married couples derives from the Supreme Court decision in Murphy vs. Attorney General (1980). This decision was based on Article 41.3.1 of the Constitution where the State pledges to protect the institution of marriage. The decision 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.
To the extent that there are differences in the tax treatment of the different categories of couples, such differences arise from the objective of dealing with different types of circumstances while at the same time respecting the constitutional requirements to protect the institution of marriage. Any change in the tax treatment of cohabiting couples can only be addressed in the broader context of future social and legal policy development in relation to such couples.
I have been advised by Revenue that from a practical perspective, it would be very difficult to administer a regime for cohabitants which would be the same as that for married couples or civil partners. Married couples and civil partners have a verifiable official confirmation of their status. It would be difficult, intrusive and time-consuming to confirm declarations by individuals that they were actually cohabiting. It would also be difficult to establish when cohabitation started or ceased. There would also be legal issues with regard to ‘connected persons’. To counter tax avoidance, ‘connected persons’ are frequently defined throughout the various Tax Acts. The definitions extend to relatives and children of spouses and civil partners. This would be very difficult to prove and enforce in respect of persons connected with a cohabiting couple where the couple has no legal recognition. There may be an advantage in tax legislation for a married couple or civil partners as regards the extended rate band and the ability to transfer credits. However, their legal status has wider consequences from a tax perspective both for themselves and persons connected with them.