Rev. Proc. 2021-24, page 19.

This revenue procedure provides two procedures for individuals not otherwise required to file 2020 Federal income tax returns to file returns to receive advance child tax credit payments, 2020 recovery rebate credit payments, additional 2020 recovery rebate credit payments, and third-round economic impact payments. The first procedure permits these individuals to file simplified returns. The second procedure enables these individuals to file complete returns electronically even if they have zero adjusted gross income.