On my son's 1040 column 4 of the exemptions was inadvertently left unchecked for one of his kids. As a result the IRS sent a letter asking for further payment and interest. He sent in the explanation letter that they said to do at the beginning of September. He just got another letter asking for the payment plus more interest.
Should he pay and file an amended return? Not pay and file an amended return? Write another letter? Wait? Cry?