detailed calculation of CTC and Additional Child Tax Credit
CTC = the lesser of $2,000 per child or the income tax liability (line 18 of Form 1040).
Additional Child Tax Credit = the lesser of
1) $1500 per child
2) 15% of the income that exceeds $2500
3) $2,000 per child LESS the CTC calculated above.
at the lower end of earned income, it is only the line in bold that really matters.
