@user17648715753
Look at the definition of MAGI above. It starts with AGI. The only things that are added are the Foreign Earned Income Exclusion, Foreign Housing Exclusion or Deduction, and excluded income from sources in Puerto Rico, Guam, American Samoa, and the Northern Mariana Islands. Anything else that is not included in AGI will not be included in MAGI. For most people MAGI will be the same as AGI.
I'm not sure what you mean by "tax free dividends." There are no tax-free dividends on Form 1040 or Schedule B. Most dividends are taxable and are included in AGI. Are you referring to exempt-interest dividend in box 12 of a Form 1099-DIV? Those are reported as tax-exempt interest. They are not included in AGI and are not added in to the MAGI calculation for the deduction for seniors.
Note that MAGI is calculated differently for different purposes. There are over a dozen different definitions of MAGI, depending on what it's being used for. What we are discussing in this thread is MAGI for the deduction for seniors.
