According to the Brazilian Federal Law 8.069/1990, minors under 18 years of age cannot check into hotels unless they are accompanied by their parents or a designated adult. If a minor is accompanied by an adult other than his parents, it is necessary to present a written authorisation for the minor to check into the hotel.
Such authorisation must be notarised and signed by both parents, and presented along with notarised copies of their IDs.
All minors under 18 years of age also need to present a valid ID with photo, to prove their identity and that of his/her parents. This must be presented even if a minor is accompanied by his/her parents.