For 2018, if you have earned income, and have a modified AGI of not more than...
... you may qualify for the Earned Income Credit. This credit is calculated automatically. It is a refundable credit, meaning you can receive it back even if you had no taxes withheld and didn't need to file a return. The credit is not available if you are married and filing separately.
A "qualifying child" is generally your son,
daughter, grandchild, stepchild or foster child, who was under age 19 at year
end (under 24 if a full-time student for at least part of five months of the
year). He or she must have lived with you in your home for more than six months
of the year, counting temporary absences for school or vacation. A child who is permanently
and totally disabled also qualifies, regardless of age.