You must amend if you are changing from deductible to non0-deductible to remove the deduction. Otherwise if nothing else would change, there is no need to amend.
There is a $50 penalty, but the IRS often waives that and will bill you if they do not.
"Penalty for Not Filing
If you are required to file Form 8606 to report a nondeductible contribution to a traditional IRA for 2017, but don’t do so, you must pay a $50 penalty, unless you can show reasonable cause." Just request a waiver of the penalty.
https://www.irs.gov/pub/irs-prior/f8606--2017.pdf
https://www.irs.gov/pub/irs-prior/i8606--2017.pdf
**Disclaimer: This post is for discussion purposes only and is NOT tax advice. The author takes no responsibility for the accuracy of any information in this post.**
