Ask Social Security Questions and Get Answers ASAP
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They did not reduce your social security benefit. What happened is that they are now deducting your Medicare Part B. The premium is based on your income in 2014. From the information you have provided, your Medicare Part B Premium is $243 (See first link below). This would imply that if single, your income in 2014 was between $107K and $160K. You can contact the Social Security Administration and potentially get the premium reduced by filing Form SSA-44. 2nd link below.
Hope this helps.