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Do you have the correct taxable amount on Form 1040 Line 4b. ?
If that is all true then only Form 8606 has to be attached.
After you e-File,
get Form 1040-X from IRS website and mail it in with your <year> 8606, which you can also get in fillable PDF
Note: when you are not changing any dollar amounts on your amending 1040-X, you can leave all the lines 1-23 EMPTY.
Part II explanation: "Did a conversion but didn't include Form 8606 with e-File".
Done this way, you sign 1040-X, not 8606.
Do not include your old 1040 nor your revised 1040 because they are identical.
@PCD21
