If you have even $400 of self-employment income you are required to file a tax return and pay self-employment tax for Social Security and Medicare. If you are a W-2 employee you do not "have" to file a tax return unless you earn more than the standard deduction amount for 2022 of $12,950.. BUT---if federal and/or state tax is withheld from your earnings then you would still want to file a tax return in order to seek a refund, even if your earnings are less than the standard deduction amount.