It is a confusing topic.......Since you have already filed, you will need to amend your 2018 return if there are any earnings on the excess + enter the 2019 1099-R on next year's return. See <a rel="nofollow" target="_blank" href="
https://www.irs.gov/publications/p590a#en_US_2018_publink1000231027">https://www.irs.gov/publication...>
