To be considered a common law relationship in Ontario a couple must have been cohabiting for 3 years, according to Haber Lawyer. A court can declare a couple to be common law spouses after 3 years, with a few exceptions.
Individuals who are already married can't be in a common law relationship until they are divorced. Couples who break up and cease cohabiting temporarily may also be considered an exception to the 3-year rule.
A couple can qualify as a common law relationship without necessarily cohabiting for 3 years if they have a natural or adopted child together, notes Ontario Family Law.