I believe the actual earnings on the excess contribution simply needs to be reported as income for the year in which the original IRA contribution was made.......per TaxAct:
If your total IRA contributions (both Traditional and Roth combined) are greater than the allowed amount for the year in your situation, and you have not withdrawn the excess contributions, you must complete Form 5329 to calculate a 6% penalty tax on the excess contribution. This penalty tax will continue to be assessed every year on ALL excess contributions (those from prior years along with any in the current year) until you withdraw the excess contributions.
Avoid this tax by withdrawing any excess amount before the due date. Note that any earnings (interest or other income) on the withdrawn contributions must still be included in gross income.
