Under family law, the general definition of a common-law partner is that the parties have to cohabit for 3 years or have a child together and be in a relationship of some permanence. This definition is very important for the purpose of determining spousal support rights and obligations.
The Income Tax Act has a different definition for a common-law partner, which includes “a person who cohabits in a conjugal relationship with the taxpayer and
(a) has so cohabited throughout the twelve-month period that ends at that time, or
(b) would be the parent of a child of whom the taxpayer is a parent. ..
and… they are …deemed to be cohabitating in a conjugal relationship unless they were living separate and apart at the particular time for a period of at least 90 days… because of a breakdown of the conjugal relationship”.
The rules above apply to married couples as well. However, if a married couple separates but does not divorce, they still continue to be related and may avail themselves of the benefits of the ITA. If a common-law couple separates, their relationship continues to exist for tax purposes only for 90 days after they cease living together, following which they cease to be “related” for the purpose of the ITA.
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