Can I join a tour group if my ID card is over 18 months or less?

No, parents need to sign up and sign a travel contract.

In order to ensure that the travel contract has legal effect, both parties must be adults aged 18; If the students are under the age of 18, parents can sign up and sign a travel contract on their behalf. If students organize their classmates to join a tour group, but their parents can't take the time to sign up for them and sign a travel contract with the travel agency, they can provide their parents' consent, attach a copy of their ID cards and autograph, and the parents of other students will sign a formal travel contract with the travel agency as representatives to ensure the legitimate rights and interests of tourists.