What do you want to do? You can file a competing return and let the IRS sort it out. You can have your son file an amended return. Either way, you cannot e-file. You will have to mail your return. You do not need to wait for his amended return to be processed, you can file now.
2020 is a complicated year because non-dependent students can get up to $1800 recovery rebate credit (stimulus money). What's not clear is how effective the IRS will be at rejecting unqualified claims.
On the other hand, the parent loses the $500 other dependent credit, as much as $2500 education credit and maybe Earned Income Credit.
There's a new urban myth among college students that says they can get a $1000 from the government just for filing a tax form. For most of them, they simply aren't eligible. A full time unmarried student, under age 24, even if you don't qualify as a dependent, is only eligible for the refundable portion of the American Opportunity Credit if he supports himself by working. You cannot be supporting yourself on parental support, 529 plans or student loans & grants. You usually must have actually paid tuition, not had it paid by scholarships & grants. It is usually best if the parent claims that credit.
You cannot claim a credit if you are, or can be, claimed as a dependent by someone else.
