If the regular distribution equal to the amount of the 2017 excess contribution is made in 2020, it will be reportable on your 2020 tax return.
This deadline to remove this excess from your Roth IRA to avoid another 6% penalty for 2019 was December 31, 2019. The deadline for obtaining a return of contribution before the filing deadline only applies to the tax year for which the excess contribution was made. In this case the applicable extended filing deadline was October 15, 2018 for the 2017 tax year.
