http://biztaxlaw.about.com/od/businessplan/f/sources-uses.htm (Sources and Uses Explained)
http://www.irs.gov/taxtopics/tc751.html (Add backs using current Social Security and Medicare Withholding Rates)
As of 8/12/2015 - The current tax rate for Social Security is 6.2% for the employer and 6.2% for the employee, or 12.4% total. The current rate for Medicare is 1.45% for the employer and 1.45% for the employee, or 2.9% total
Only the Social Security tax has a wage base limit. The wage base limit is the maximum wage that is subject to the tax for that year. For earnings in 2015, this base is $118,500.