A child travel consent form is strongly recommended if a child travels alone, with only one parent or an authorized adult. Children under 18 may need a Letter of Consent to travel internationally without both parents.Country-specific regulations. This article explains the form a nonparent can use to grant an adult caregiver the authority to make decisions for a child. The intention of this letter is to provide consent for a minor child to travel without the company of both legal parents. The officer said we should always travel with a notarized letter from his parents authorizing travel and to authorize medical care if needed. This guide includes forms and instructions for a letter and affidavit to request that the court register an out-of-state custody order in Texas. This guide includes forms and instructions for a letter and affidavit to request that the court register an outofstate custody order in Texas. However, if she is traveling with only one parent, a letter of consent from the other parent or a copy of the custody document is required. The most common interpretation is that the traveling parent requires a notarized letter something not found in any custody order.