If you are talking about paying the 6% penalty on excess contributions carried over to next year, this amount is calculated on form 5329 and is automatically carried to line 6 on Schedule 2 of your 1040.
If you are talking about having to pay income tax on the excess contributions, note that the excess amount is automatically added to line 8 (Other Income) on Schedule 1 (1040), so it is added to your taxable income.
[Edited 4/2/2020 11:26 am CDT - updated for 2019]
