1099-R box 7 code is J but the distribution is from contribution not earning

[hebegg]

I did not file my 1099-R 2017 (from Fidelity) last year as the distribution is from my contribution, but not any earnings. However today I received a mail from IRS saying that I my 1099-R has such distribution and I owe the tax. I checked my 1099-R and the box 7 is indeed 7. 

In the mail it also says if you think the full amount is not taable, complete the appropriate part of Form 8606. I understand I should fill out the basis for it. But do I need to show the statement (where I deposit the money via cash) or I need some other proof from Filidelity? 

[dmertz]

Form 8606 Part III is required to be included with your tax return for any nonqualified distribution from a Roth IRA.  Unless the IRS asks for more, this is the only thing needed to demonstrate that your distribution nontaxable.  Over the years the IRS and you have been provided with Forms 5498 from your Roth IRA custodians showing the amount you have contributed for each year, so there is normally no need to provide the IRS with anything beyond the missing Form 8606.