Final answer:
Salary deductions for Social Security are capped at 12.4% up to the wage limit of $118,500 as of 2015, with Medicare taxes fixed at 2.9% without any wage ceiling. Federal income taxes operate under a progressive tax structure, increasing with income levels.
Step-by-step explanation:
The limit on the amount of salary deductions that may be made for Social Security is at a rate of 12.4% up to a certain wage limit. In 2015, this wage limit was set at $118,500. It is important to note that Medicare tax is fixed at 2.9% with no upper ceiling, covering elderly healthcare. Federal income tax rates increase with income up to certain levels, and this progressive tax structure is separate from the fixed percentage rates of payroll taxes for Social Security and Medicare.