Sorry I have to disagree. I think the prior replies were missing the point of your question. Is box 5 the same as box 3? Yes the Medicare Premium deduction is included in the Net Benefits in box 5. So they will be part of any taxable Social Security amount. But no they are not income or taxable by themselves. If the Medicare premium was not included in box 5 benefit income then you wouldn't be able to deduct them on Schedule A as an itemized deduction.
