The IRS didn’t give any reason, stated that the prove of tax withheld amount and income. My tax is very simple, so I sent a copy of 1099-R (there is a tax withheld on it), and all the supporting documents: my dividend and interest, that all I have. All by mail, cause I don’t have fax machine.
Thanks , I have checked the IRS online “where is my refund” every day since I have mailed my supporting documents on June.
