A child travel consent form is strongly recommended if a child travels alone, with only one parent or an authorized adult. A notarized letter of consent is a crucial requirement when traveling with minors without both parents or guardians.If children are not travelling with both their parents, (ie: if they are travelling alone, or with another adult), this form can be used to give permission. No, it is not legal for one parent to leave the US with a minor child without the consent of the other parent. Parental consent is not required for in-state travel. The easiest way to obtain consent is to have it written in to a child custody agreement. I was asked to present the consent form at immigration when I was returning home from the Bahamas with my grandparents. I was 15 at the time. The most common interpretation is that the traveling parent requires a notarized letter something not found in any custody order. If children are not travelling with both their parents, (ie: if they are travelling alone, or with another adult), this form can be used to give permission.