For the deduction for seniors in the new tax law, MAGI is Adjusted Gross Income (AGI), Form 1040 line 11, plus the Foreign Earned Income Exclusion and excluded income from sources in Puerto Rico, Guam, American Samoa, and the Northern Mariana Islands. So, to answer the question in your other post, the taxable portion of Social Security benefits is included, since it is included in AGI.
