Children under the age of 16 traveling between the U.S. and Canada without both of their parents or a legal guardian are considered "unaccompanied minors" and require special permissions at the borders of both countries to prevent abductions and runaways. For the purpose of special border regulations when entering the U.S., "children" are considered to be 15 and younger, while adolescents between 16 and 18 abide by the same requirements as adults. When entering Canada, "children" are defined as 17 and younger.
Minors traveling alone between the United States and Canada may present a valid passport at any border crossing. For air travel, a passport is the only acceptable identification, regardless of age. If you are a citizen of either country, you do not need a visa to travel for study or tourism.
A birth certificate or other nationally recognized non-photo ID is sufficient for minors 15 and under crossing into the U.S. by land or sea. The U.S. accepts a Consular Report of Birth Abroad, a Naturalization Certificate, or a Canadian Citizenship Card as additional forms of valid identification for minors. Children between 16 and 18 entering the U.S. are required to travel with a passport, just like adults. When entering Canada, a birth certificate is required in addition to a passport for anyone under 18.
Letter of Consent
Upon entering the U.S. or Canada, children must have a letter of consent signed by both parents that authorizes the minor to travel alone. The letter must have both parents' names, addresses and telephone numbers, as well as the name, address and telephone number of the adult who will be responsible for the child in the country he is visiting. A sample consent form is available from Canada's Department of Foreign Affairs and International Trade. U.S. Customs and Border Protection recommends that the parental consent letter be notarized, although this is not an official requirement.
If only one parent has signed the consent form, children must have documents proving custody court orders, a death certificate or any official document that explains why only one parent is legally responsible for the child. If a guardian is signing the custody papers, documentation to prove that the guardian has legal custody is required.