Is it better for my daughter to fill out her taxes as single or common-law? She and her partner both finished University last year and are newly common-law.

As per the Canada Revenue Agency (CRA): 

Living common-law means that you are living in a conjugal relationship with a person who is not your married spouse, and at least one of the following conditions applies:

• This person has been living with you in a conjugal relationship for at least 12 continuous months

Note
In this definition, 12 continuous months includes any period you were separated for less than 90 days because of a breakdown in the relationship.

• This person is the parent of your child by birth or adoption
• This person has custody and control of your child (or had custody and control immediately before the child turned 19 years of age) and your child is wholly dependent on them for support

If this is not the case, she will be claiming as single this year.

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