my son is in college and worked a summer sales job in a different state. He was living in an apartment for 2 1/2 months, paid for by his company. He had the pay for food, kitchen supplies and any other living necessities. His company had each employee purchase a gym membership and requested the team work out each morning before going to work. He received a 1099-NEC and made approx 10,000. He didn't have a car up there.
I filed his taxes, he owed 1,500 (for the self employee tases) plus another 450 in state tax.
My question is can I amend his tax form and include any business deductions for food, the gym and living necessities to reduce the amount of tax owed? (reduce the amount paid, since we paid them all yesterday with online filing)
Yes, you can always amend and add business expenses, if you have any. Expenses that are ordinary and necessary for that type of business are deductible. The gym membership might be deductible.
Paying rent and buying food are normal expenses. Travel expenses are a different story. It doesn't sound like he was not traveling though, just went to one spot to work.
You know more about what he did, see Deducting Expenses.