Several options.
1) Do you think you will be under the income limit in 2021 for the excess amount. If so you can just apply the excess as a 2021 contribution.
2) A safer method is to have the account trustee return the excess and the earnings attributed to the excess as a "return of contribution" before the April 15 due date (be sure it is a return of contribution and not just a normal distribution so the resulting 1099-R will be coded correctly). The trustee will issue a 2021 1099-R that you will receive in January 2022. Only the earnings returned will be taxable.
3) You can have the trustee recharacterize the excess plus earnings to a Traditional IRA as a non-deductible contribution (or possible deductible if your MAGI is within the deduction limits). In this case there is no tax at all as the earnings simply move to the Traditional IRA. Again this must be done by the April 15 due date.
**Disclaimer: This post is for discussion purposes only and is NOT tax advice. The author takes no responsibility for the accuracy of any information in this post.**
