A child can be a parent’s dependent if under age 24 and a full-time student who does not provide more than half of his/her support. A full-time student means the child is enrolled in school on a full-time basis for at least part of five months during the year. You must decide whether your son meets these tax requirements to be treated as your dependent.
On Form 1040X, you may file an amended return within a three-year period to claim a refund or correct a mistake made on an original or previously amended return.