Required Minimum Distributions (RMDs) are mandatory annual withdrawals from traditional IRA, 401(k), 403(b), and similar tax-deferred retirement accounts. They start at age 75 under SECURE 2.0 (was 72 before, 70½ before that). The IRS forces you to start withdrawing — and paying tax on the withdrawals — whether you need the money or not.
Calculation: the IRS publishes a Uniform Lifetime Table with a 'divisor' for each age. RMD = prior year-end account balance ÷ divisor. At age 75, divisor is 24.6 — so 1/24.6 of the balance, or about 4.07%. At 85, divisor is 16.0, so 6.25%. Each year you take a higher percentage as the divisor decreases.
Roth IRAs do NOT have RMDs during the original owner's lifetime. Roth 401(k)s used to have RMDs but SECURE 2.0 eliminated them starting 2024.
Penalty for missing an RMD: 25% of the amount you should have withdrawn (was 50% before SECURE 2.0). If you correct within 2 years, drops to 10%. So missing an RMD is genuinely expensive.