Information on children travelling without both parents
We strongly recommend that Canadian children carry a consent letter if they are travelling abroad alone, with only one parent/guardian, with friends or relatives or with a group. For the purposes of this consent letter, a Canadian child is defined as anyone who is under the age of majority (18 or 19, depending on the province or territory of residence).
A consent letter is not a legal requirement in Canada, but it can simplify travel for Canadian children, as it may be requested by immigration authorities when entering or leaving a foreign country or by Canadian officials when re-entering Canada. The letter demonstrates that Canadian children have permission to travel abroad from parents or guardians who are not accompanying them.
Article Courtesy: https://travel.gc.ca/travelling/children/consent-letter.