It depends. Since he is working from home, he may be able to claim home office expenses. Here is an FAQ with more information (and follow the link to the Home Office Deduction for his business or as an employee is pay is reported on a W-2): https://ttlc.intuit.com/replies/3302005
There are other things, such as his computer, (the percentage that he uses for business), office supplies, registrations, licenses, advertisement, and a number of other categories that could produce deductions. See this FAQ if he is self-employed: https://ttlc.intuit.com/replies/5559255
And this FAQ if he is an employee: https://ttlc.intuit.com/replies/3300622
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