How do we correct for a missed prior year Roth IRA contribution?

[bnrfischer]

We forgot to post a Roth IRA contribution that we made in 2015... how do we correct this omission so that our cost basis will be correct hence forth?

[MiriamF]

You may need to amend your return for 2015 to file Form 8606, Nondeductible IRA Contributions.

These instructions for correcting your Roth basis are rather old, but they still apply. Give them a try (the names of some of the pages may have changed a bit), and if they don’t work, please write back.

This is how to amend a 2015 return.