As per Canada Revenue Agency (CRA), an individual is considered to be resident in the province where he or she has significant residential ties. An individual who is resident in more than one province on December 31 of a particular tax year will be considered to be resident only in the province in which the individual has the most significant residential ties, for purposes of computing his or her provincial tax payable.
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If your son was a resident of British Columbia on December 31, 2022, but lived in Alberta for 6 months in 2022, then you would report his residency as British Columbia for tax purposes.
Individuals are considered residents of the province or territory where they have significant residential ties, such as a permanent home, dependents, or personal property. Based on this definition, it appears that your son's significant residential ties were in British Columbia, even though he spent 6 months living in Alberta for hockey.
For more information please see Canada Revenue Agency(CRA) Website. Your province or territory of residence