Your Pension and Social Security Benefits
The amount of your Social Security benefits are mainly determined by how long you've worked and paid into the Social Security system. Most employees have Social Security contributions automatically deducted from their paychecks (public school teachers and other public employees are an exception). Pension plans are offered and maintained by your private employer, based on years of service and salary. Many retired people draw both Social Security benefits and a monthly pension check.
Despite a popular misconception, however, receiving a pension does not automatically reduce your Social Security benefits. See FindLaw's Social Security Basics and Retirement Planning sections for related articles and resources.
I am receiving, or will be receiving, a pension, does this affect how much I can expect to receive from Social Security?
Generally, no. Both pensions and Social Security require you to "pay in" in order to receive the benefit of these retirement systems. If you've been paying into Social Security during your working life, then your pension won't necessarily reduce your Social Security income. Generally, any money you have already earned cannot be taken away.
What can sometimes happen, however, is that a person was not paying into Social Security for a period of time, but was paying into a pension, which can cause confusion. If you did not pay into Social Security because you worked for the U.S. civil service, some state and local governments, or for a foreign employer who wasn't required to pay in to Social Security, then you will see a reduction in your Social Security benefits. Your reduction in benefits is based on the time period you didn't pay, however, not on your pension. Statements from the SSA itemize how much you have paid into the program and what you may be eligible to collect when you retire.
If you did not pay in to Social Security for a while and want to calculate the reduction in your benefits, read the SSA article Windfall Elimination Provision [PDF], also known as Publication No. 05-10045, which will explain how to calculate a reduction.
Consider speaking with a Social Security attorney if you have additional legal questions pertaining to your retirement benefits.