Under the Affordable Care Act (ACA), eligibility for Medicaid, premium tax credits or premium subsidies, and cost-sharing reductions or  is based on modified adjusted gross income (MAGI). But the ACA has its own calculation of MAGI, which differs from MAGI calculations used for other purposes. The details of the MAGI calculation are outlined here. If you have questions or want guidance about your particular circumstances, consult a tax advisor or other professional. MAGI starts with adjusted gross income (AGI) from Form 1040, but three things must be added to AGI to get MAGI under the ACA. If applicable, you must add in these amounts: Non-taxable Social Security benefits (this includes Social Security Disability Insurance benefits (SSDI), but Supplemental Security Income (SSI) does not get counted when the ACA-specific MAGI is determined) Tax-exempt interest (typically earned on municipal bonds) Foreign-earned income and housing expenses for Americans living abroad