With 1 week to go we now need to consider the scenario that refund won't be issued or will be issued past 7/15, so most of the answers above no longer applies.
TurboTax gave a clear example (READ last sentence of paragraph 1) that even past tax deadline, one can still request and get refund for the excess contribution.
Does the double tax scenario mean you will be
1. Taxed in 2019 for excess contribution by reporting income on Line 1.
2. Taxed again when retire and take distribution
But if you already took refund, then there is no more tax on that refunded amount. What does double tax mean?
"Example 2:
Assume same information as Example 1. But Jessica doesn't discover the overpayment until November 20, and she had already filed her 2019 return. She notifies the plan administrator immediately, and she withdraws the excess on December 5.
Jessica must pay additional taxes on the overpayment because she didn't withdraw the funds by April 15. She amends her 2019 return to report the overpayment as if she received Form 1099-R (same as Example 1) and pays the additional taxes.
On her 2020 return, Jessica enters the forms she received from the plan administrator. Only the earnings on the overpayment will be added to Jessica's 2020 income."
