It is not clear what you are wanting to do. If you worked as an independent contractor and earned even $400 you need to pay self-employment tax for Social Security and Medicare. Why are you asking about paying self-employment tax on "other" income? What kind of income are you asking about?
https://ttlc.intuit.com/community/self-employed/help/what-is-the-self-employment-tax/00/25922
**Disclaimer: Every effort has been made to offer the most correct information possible. The poster disclaims any legal responsibility for the accuracy of the information that is contained in this post.**
