A cohabitation agreement is a form of legal agreement reached between a couple who have chosen to live together (whether they are heterosexual or homosexual). In some ways, such a couple may be treated like a married couple, such as when applying for a mortgage or working out child support. However, in some other areas, such as property rights, pensions and inheritance, they are treated differently.
A cohabitation agreement contains documentation for a couple who want to live together in order to protect themselves from unnecessary cost and litigation should their cohabitation break down. They can clearly regulate their property rights and what arrangements might be made for mutual financial support, dealing with debt, caring for children, etc.
The agreement also, much like a prenuptial agreement, allows the individuals concerned to determine in advance who will keep specific assets and what will happen to assets that have been purchased jointly if they separate. This agreement is intended to bind both parties.
In the United States, about 15 million couples qualify as cohabiting. A cohabitation agreement can give each party an idea of the expectations of the relationship with the legal enforceability to protect against financial ruin or the loss of support that was promised. It is a good idea in that if the couple does break up, an altercation about who receives what may be less likely. However, the courts may occasionally change or ignore provisions set out in a cohabitation agreement if they feel that they are inadequate under the circumstances.
Cohabitation agreements are not considered to be legally binding in the United Kingdom.
A cohabitation agreement will usually not be adequate to settle all legal issues that might arise, so a trust deed setting out property rights and a will are also recommended.
It is a common misconception that there is a doctrine of "Common Law marriage" in English law. That is to say that without having married, there is no automatic right to home ownership, even if the home is shared for a long time. Instead, the only way in which ownership can be obtained is through ordinary trust law. Interestingly, even if the parties are legally married, there is still no automatic right to home ownership. Instead, any transfer of ownership will be at the discretion of the court when exercising their power under the Matrimonial Causes Act 1973.