From IRS:
For 2021, the EITC is generally available to filers without qualifying children who are at least 19 years old with earned income below $21,430; $27,380 for spouses filing a joint return. The maximum EITC for filers with no qualifying children is $1,502, up from $538 in 2020. There are also special exceptions for people who are 18 years old and were formerly in foster care or are experiencing homelessness. Full-time students under age 24 don't qualify. There is no upper age limit for claiming the credit if taxpayers have earned income. In the past, the EITC for those with no dependents was only available to people ages 25 to 64.

PROSERIES Support:  I just filed tax for a client who was 23 and was a full time student.  I even entered his 1098-T and marked him as a full-time student.  Software still qualifies him for EITC on his 1040!!!   Is this correct or software is all messed up?