The Earned Income Tax Credit is built specifically to reward work, which is why its core requirement is right in the name: you have to have earned income — wages, salaries, tips, or net self-employment earnings — to qualify at all. Income from investments, pensions, or unemployment alone doesn't count as earned income for EITC purposes. * There's a cap on investment income specifically: if your investment income (interest, dividends, capital gains) exceeds a set annual limit, you're disqualified from claiming the EITC entirely, regardless of how low your earned income is. * Social Security numbers matter here in a way they don't for every credit: you, your spouse if filing jointly, and any qualifying child you're claiming for the credit all need valid Social Security numbers issued by the tax filing deadline, including extensions. An Individual Taxpayer Identification Number doesn't satisfy this requirement. * You don't need children to qualify, which surprises a lot of people who assume EITC is only for parents. Filers without qualifying children can still claim a smaller version of the credit, but they face an age requirement that parents don't: you generally have to be at least 25 but under 65 by the end of the tax year, and if married filing jointly, at least one spouse needs to meet that age range. * Income limits for the credit scale with both your filing status and how many qualifying children you claim — more children generally means a higher income ceiling before the credit phases out entirely, which is why two families with identical incomes but different numbers of kids can have very different EITC eligibility.