A cohabitation agreement is a written agreement between people in a marriage-like relationship dealing with financial arrangements during the relationship or in the event of a relationship breakdown. A cohabitation agreement can be made between people who are not yet spouses (either married or common-law), or who are already married or common-law spouses. Generally, in order for a cohabitation agreement to be valid it must be in writing, witnessed, and signed. However, there are circumstances in which a cohabitation agreement, or parts of it, may not be valid. You should consult with a lawyer to ensure that your specific situation is properly addressed in a cohabitation agreement.