Children 15 years of age and under are now required to show proof of citizenship (a certified copy of their birth certificate is acceptable). They are not required to show photo ID. If you are travelling with children, you should carry identification for each child. Divorced parents who share custody of their children should carry copies of the legal custody documents. Adults who are not parents or guardians should have written permission from the parents or guardians to supervise the children. When travelling with a group of vehicles, parents or guardians should travel in the same vehicle as the children when arriving at the border. Customs officers are looking for missing children and may ask questions about the children who are travelling with you.