Can I file my son 20 as a dependent who lived with me last year until october, went to school for 3 month full time but earned more than $5050 by end of 2024?

duplicate

No.  Since he only went to school for 3 months he does not meet the requirements of being in school full time for 5 months, which would disqualify him as a qualifying child.

Since he made more than $5,050 he does not meet the criteria to be a qualifying relative. 

The following criteria must be met to claim someone as a qualifying child:

• Your child (including adopted and foster children), your sibling, or a descendent of any of them.
• Age 18 or younger at the end of the tax year OR under 24 (and younger than you and your spouse) if they are a full-time student
• Lived with you for more than 6 months during the tax year
• They did not provide more than half of their own support (social security does not count)
• They did not file a joint return, unless it was to claim a refund
  
   

To claim someone as a Qualifying Relative, they must be:

• Your child ( including step children, adoptive children and foster children) or a descendent of them
• Your sibling (including half siblings) or a child of your sibling or a sibling-in-law
• Your parent or grandparents, including step parents and in laws
• Any other person that lived with you for the entire tax year
• Not a qualifying child of another taxpayer
• Someone that you provided over half of their support for during the tax year
• Has less than $5,050 in income (not counting social security)