Ontario and the 18 provinces. In Alberta, Manitoba, Ontario, Prince Edward Island and Saskatchewan the age of majority is 18, so a person is legally an adult on their eighteenth birthday and, strictly, no longer needs a consent letter. The practical advice still runs the other way. The Canadian government recommends carrying a letter for any traveller under 19, because foreign border officers apply their own thresholds and a 17 or 18 year old is routinely asked for one. An Ontario notary, commissioner for oaths or lawyer can witness the signature, and Ontario families should note that a single letter may list all siblings who share the same two parents.
British Columbia and the 19 provinces. British Columbia, New Brunswick, Newfoundland and Labrador, Nova Scotia and the three territories set majority at 19 under each jurisdiction's Age of Majority Act. A child of 18 in these provinces is still a minor for provincial purposes, which reinforces the standing recommendation to prepare a letter for anyone under 19. Witnessing options are the same, and a notary public is the usual choice for cross-border documents.
Blended and separated families anywhere. The sharpest regional variable is not geography but custody. Where parents have separated, the parent who is not travelling and who holds parenting time or decision-making responsibility should sign, and the letter travels with the separation agreement or court order that defines those responsibilities. This template is drafted for the common-law provinces and territories; Quebec's Civil Code regime, with its own rules on parental authority and tutorship, is not covered here.