Due to earning more than the minimum limit my 20 year old son did not qualify as a dependent. Does he need to file his own tax return?

If he was a full time student you can still claim he no matter how much he made.

Yes, he will file his own tax return if he is required to file or if he had income tax withheld. 

Please view the filing requirements below.

https://ttlc.intuit.com/replies/3302274