U.S. Yahoo Finance analysis points out that the U.S. Social Security Administration (SSA), when evaluating eligibility for retirement benefits, only counts wages and self-employment income in its earnings test, excluding 401(k) withdrawals. However, the U.S. Internal Revenue Service (IRS), when calculating taxable income, includes both 401(k) withdrawals and self-employment income in "provisional income," which could lead to up to 85% of Social Security benefits being taxed. Furthermore, large 401(k) withdrawals could trigger income-related monthly adjustment amounts (IRMAA) for Medicare two years later, resulting in higher Medicare premiums.