first of all, do not send in an amended 1040x until your original 1040 has been processed by the IRS- that is, if you have a refund coming, wait until the refund hits your bank account- if your refund is coming as a check, wait until you have deposited the check into your bank. Only then do you file the amended return. The only thing you send is the amended 1040x, and, if you owe money, include the check (do not use a payment voucher). Just the 1040x and a check (if you owe). That is all.
