Do you have the correct taxable amount on Line 4b?
E-file your return, don't file on paper.
After it is ACCEPTED,
get Form 1040-X from IRS website and mail it in with your 8606, which you can also get in fillable PDF.
Note: since you are not changing any dollar amounts on your amended tax return, you can leave all the lines 1-23 EMPTY.
The names on 8606 should be "<owner> and <your name> BENE" or Beneficiary if it fits, and your SSN.
Part III explanation: "didn't include Form 8606 with e-File".
You will have to mail it so this does not use up your one 1040-X e-File.
In a few months to a year, you will get an acknowledgement from the IRS.
