If you are self-employed, you will need to file Schedule SE (Form 1040) to figure out the tax due on net earnings from self-employment ¹². This tax applies no matter how old you are and even if you are already getting social security or Medicare benefits ¹. You must file Schedule SE if the amount on line 4c of Schedule SE is $400 or more . If you filed Form 4029 or Form 4361 and received IRS approval, you may not need to file Schedule SE ¹.

Please note that this is a general guideline, and you should consult a tax professional for specific advice regarding your business and tax situation.