It depends on how you're paid.  

If you're paid as an employee -- for which you should receive a Form W-2 -- then your Social Security and Medicare withholding should have been taken out of your pay and reflected on the W-2.

If you received a Form 1099-MISC reflecting your earnings -- or received no IRS form at all -- you're probably an independent contractor and will need to pay self-employment tax if your net self-employment earnings are over $400.  

Please see the TurboTax FAQs "Am I considered self-employed?" and "Does a 1099-MISC mean I'm self-employed?" for more information.

https://ttlc.intuit.com/replies/4771022

https://ttlc.intuit.com/replies/4770969