The Government of Canada strongly recommend that Canadian children carry a consent letter if they are
(a) travelling abroad alone,
(2) with only one parent/guardian,
(3) 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.
For more information and sample letters, please visit https://travel.gc.ca/travelling/children/consent-letter