I made less than $5,000 of taxable income in 2018. However, I invested some of that into the stock market. Do I still need to file taxes for the 2018 tax year?
If you were salaried you could file for any tax withheld and if you are not a dependent you might qualify for earned income credit. If you got a 1099-misc with income in box 7 you have to file to pay self employment tax.
