Using the Desktop software.....You can create many tax files.
You have to create a NEW tax file for him...you do not add his W-2 to your MFJ tax return. Save your MFJ tax return, and then start a NEW tax return on the Desktop software's home page.
1) ........you still claim him as a dependent on your own tax forms.
2) ......on his new tax return, yo have to make sure you indicate that he can be claimed as a dependent by someone else. Make sure you e-file you won MFJ tax return before his anyhow...to avoid complications.
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Whether he has to file at all depends a lot on the types, and his total income for the year....and even if he doesn't have to file, he can't get any $$ in box 2 of the W-2 refunded unless he does file.
https://ttlc.intuit.com/community/filing-and-paying-taxes/help/do-i-need-to-file-a-federal-return-this-year/01/25546