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Our situation is the opposite.  My 26-year-old son made just $1,000 working and lived with us the entire year. When he completed his return he stated someone else (my husband and I) could claim him as a dependent. He filed on time and received a nominal refund. My husband and I filed an extension, but now as we are working on preparing our taxes, we find we should NOT claim him as a dependent.  I know we can just remove him from our personal section, but should he file a 1040X? He'll get a bit more back from the IRS and, more importantly, his return would be corrected, right?