The Model of Income in the Near Term, Version 8 (MINT8) is a tool developed for the Social Security Administration to project future retirement incomes and analyze the distributional effects of Social Security reform proposals. MINT8 expands on earlier model versions by adding work-related expenses, child care costs, child support payments, and homeowner with a mortgage status, which are used to estimate supplemental poverty rates. MINT8 also updates several model components to use more recent data and account for changes in income and assets through the Great Recession. MINT8 starts with pooled 2004 and 2008 Survey of Income and Program Participation data linked to administrative earnings and benefits records through 2015. MINT8 projects outcomes through 2099 for the 1905 to 2067 birth cohorts. Projections include marriage, divorce, and mortality; immigration and emigration; labor force participation and earnings; disability and health status; retirement and Social Security benefit take-up; employer benefits and work history; income from defined-benefit pensions and accruals in defined-contribution retirement accounts; financial and housing wealth; Supplemental Security Income eligibility and benefits; other government benefits; total family income; payroll, federal, and state income taxes; Medicare surtax; work expenses, child care expenses, and child support payments; out-of-pocket spending on health insurance premiums and medical services; and official and supplemental poverty rates.