The ACTC is calculated on form 8812 and is basically 15% of your earned income over $2500. The ACTC is a maximum of $1700 (2024) (per child, not $2000).
What's on lines 18, 19 and 28 of form 1040? If $0 tax on line 18, there will be $0 Child tax credit (CTC) on line 19. So, you get the maximum $1700 Additional CTC on line 28 (assuming you have enough earned income).
