While a parent can technically pay for and "book" a hotel room for an 18-year-old, the ability for the 18-year-old to actually check in depends strictly on the hotel's individual minimum age policy. In many parts of the world, 18 is the legal age of "majority," meaning the guest is an adult and can check in without issue. However, in the United States, many hotels—particularly in major cities or "party" destinations like Las Vegas or Miami—have a minimum check-in age of 21 or even 25 to mitigate liability and noise concerns. If the hotel’s policy is 21+, an 18-year-old will be denied check-in even if the room is fully pre-paid by a parent. To facilitate this, parents can often fill out a "Credit Card Authorization Form" in advance to cover the costs, but this does not override the age requirement. If your 18-year-old is traveling alone, it is vital to call the hotel directly before booking to confirm their specific check-in age. If the policy is 21+, you should look for "student-friendly" hotels or hostels that explicitly cater to the 18-20 demographic to ensure they aren't left without a room upon arrival.