The earned income credit is first calculated (actually looked up in a table) on your earned income then it is calculated on your total income (AGI). You get the lesser of the two calculated EIC numbers. See the 2024 EIC table at:
https://www.irs.gov/instructions/i1040tt#idm140702909059168 scroll way down
So, for example, taking a deduction (adjustment to income) for an IRA contribution will not make you eligible for EIC, if your earned income made you ineligible.
