@Tremaine2 wrote:
I have to amend the 8606's back to 2016...you're saying I can file 1040-X w/8606 even beyond the time a return may be amended? No changes are required on any of the 1040's themselves--only Form 8606 lines 1, 2 and 3 need to be amended to correct the basis amounts carried forward.
Let me poll @dmertz here, who is the best expert on this topic.
You can file form 8606 alone if you are changing your basis or reporting non-deductible contributions as long as it does not change your overall tax owed or refund due. There would be no reason to file a 1040-X.
(To clarify one point: you can file an amended tax return for any year you need to correct, no matter how old. If you are due a refund, it won't be paid if the amended return is more than 3 years old, but you can still file to make needed corrections.)
It sounds like you are only updating the non-deductible basis, so I don't think you need to include a full 1040-X. I do think you would write "Amended" across the top. Send the forms in separate envelopes, and use a mailing service with proof of delivery. I don't have a strong opinion on attaching an explanation, but i think it's probably unnecessary because the IRS will be able to see that the carryovers are tracking.
