I received one 1099 from Square for all my sales for the year. The sales in NY probably comprise about less than 10% of my sales from the year.
As per the IRS language, I wouldn't say that the income was from a "New York source," as I was making sales from people from all over (i.e. I wasn't "employed" by any NY company). I am an artist and this was a small temporary popup event where I sold my artwork. I was there for two weeks and it was probably less than 10% of my total income from all sources.
And it was not income related to business previously carried on in the state, as it was my first time selling there.
So it does not seem like I need to file, but I'm not 100% sure?
You need to file a New York State (not City) return. New York does tax you because the activity was performed in New York. Georgia also taxes you, but will give you a credit for the tax you pay to New York on this income.
Where your clients are actually from is not the determining factor, but rather, where the activity took place. Since you were in New York State, you pay tax to New York state on this activity.
New York City does not tax you, however, because NYC does not tax a nonresident of NYC (which is part of the NY State return)., even though the activity was performed in NYC.