For prior year Form 8606, should I simply mail the form to IRS and wait for their response? Or should I enclose a letter ? Will I be billed later for the penalties?

just mail it and wait for a response, if any. sign each one.
Keep copies for your records.

IRS wants you to keep all 8606 forms forever.

The IRS does not acknowledge receiving the 8606 forms unless they send a bill for the $50 penalty for failing to file the 8606 each year as required.   You can include a request to waive the penalty.    I suggest mailing certified or registered mail as proof of mailing.

Thank you, I think I'll include the request and send by certified mail.

I would.  A "reasonable cause" is almost anything.

<a rel="nofollow" target="_blank" href="https://www.irs.gov/pub/irs-pdf/i8606.pdf">https://www.irs.gov/pub/irs-pdf/i8606.pdf</a>
"Penalty for Not Filing
If you are required to file Form 8606 to report a nondeductible contribution to a traditional IRA for 2018, but don’t do so, you must pay a $50 penalty, unless you can show reasonable cause.

• Form 8606 can be filed by itself when you are not required to file a tax return.*
• Form 8606 was not attached to the filed tax return, as required.
• Use Form 1040X to add or correct information on an already filed tax return.

Therefore, the 8606 should be attached to an amended tax return.

In my opinion, you would not be fined a non-filing penalty after filing an amended return for those years.

* See Instructions for Form 8606.

Hi fanfare, thanks for your reply. I read through the instructions for a prior year 8606 and it only asks (page 6) to use 1040X if one needs to make a change to previously filed 8606. I also reviewed the form 1040X for that year and there is really no material change to any data in that form. So I am going with filing 8606 by itself.

That is correct.  A 1040X is required when changing from a previously filed deductible contribution to a non-deductible contribution and visa-versa, both of which will change the taxable amount and require an amended return.   Both the 8606 instructions and 1040X instructions specify when a 1004X is required.      When only reporting a 8606 that was missed and there will be no change in the taxable amount (a tax return not required), the 8606 can be filed by itself.

a 1040X is used to add or correct information on an already filed return.
Citing one example of use of 1040X does not obviate other uses.

also  Page 6 of the instructions does not only ask for 1040X in a particular situation. That is a misreading of the instructions.

Once again we'll just have to agree to disagree.

Once again, *nothing* is "being added, or corrected" on a already filed tax return.   The 8606 form is not part of the tax return, it is filed *with* an original tax return, but is not part of that tax return.   If nothing changes on the tax return no 1040X is required to report a late 8606 - it is still the original 8606 albeit sent late.

Page 6 does say when a 1040X is required - it is when a change of previous filed form is being made.   This is not a change, it is the original 8606 just being filed late that should have been filed with the original return.  The original return is not being changed in any way.

Now, if the OP could have deducted the Traditional IRA contribution, then the OP could still amend to deduct it and would probably receive a refund, but no 8606 would be required at all.

I was not aware that forms included, or attached to a return, are not part of the tax return.
I'll have to think about that ... ...

macuser_22 and fanfare, I thank you for your thoughtful recommendations. Given that this is the IRS, there is plenty of room for alternative viewpoints and disagreements are natural. It is great to have this community to reach out to and your time and efforts are much appreciated.

I submitted a few  8606s for a few years of forgotten non-deductible IRAs. It has no impact on 1040 because I paid the taxes on the non-deductible IRAs.  It is needed  to track the basis for conversion to ROTH to avoid paying taxes twice. 

I sent just the 8606 forms.  a year later I was told by IRS to send 1040-x.  I can't figure why but I am sending the 1040-x with explanation in Part III Explanation of changes because there is no line that changes on the 1040x.  I will keep you posted if it works.

For years taxpayers have been sending stand alone 8606 forms.   It is only very recently that a few have received letters asking for a 1040X.   Perhaps the IRS has changed their procedures recently.