The Social Security wage base will be jumping to $127,200 for 2017.  That is an $8,700 increase in the taxable wage base from 2016. 

This tax is paid by both the employee and employer...it is deducted from the employees wages and the employer makes a matching contribution on behalf of the employees...each paying 6.2%. 

Self-employeds pay it as part of their self-employment tax and pay both parts, which is a combined rate of 12.4% for the social security portion of the self-employment tax.