How do changes to life expectancy tables alter RMD amounts for retirees born in different years?
Executive summary
Changes in which IRS life expectancy table applies — Uniform Lifetime, Joint Life and Last Survivor, or Single Life — directly change the divisor used to compute an RMD, so a retiree’s required withdrawal can move by several percentage points year to year (for example, age 73 corresponds to a distribution period of 26.5, i.e., about a 3.77% RMD) [1] [2]. Rules about spouse age differences, beneficiary status and the “minus‑1” method for inherited accounts create large differences: a spouse more than 10 years younger can use a Joint Life table (lower RMDs) while non‑spouse beneficiaries use the Single Life table and generally see faster pay‑outs [3] [4] [5].
1. How the math works — tables drive the percentage
RMDs are calculated by dividing the prior‑year December 31 account balance by a distribution period (life‑expectancy factor) from an IRS table; a smaller divisor raises the RMD percentage and a larger divisor lowers it (Account Balance ÷ Distribution Period = RMD) [6] [7]. For example, the Uniform Lifetime Table gives age‑based divisors such as 26.5 for age 73 (about a 3.77% required withdrawal) — that exact factor appears in IRS guidance and provider examples [1] [2].
2. Which table you use changes your RMD materially
Which one of the IRS tables applies is a rules question with real dollar effects. Married owners whose sole beneficiary spouse is more than 10 years younger can use the Joint Life and Last Survivor Table, which produces larger divisors (smaller RMDs) than the Uniform Table; most other owners use the Uniform Lifetime Table [3] [4]. Beneficiaries of inherited IRAs generally use the Single Life table, which typically yields smaller divisors (so larger RMD percentages) and accelerates distributions compared with the Uniform Table [5] [2].
3. Birth year, RMD starting age and timing matter
When you must start RMDs depends on your birth year (the required beginning date shifts with legislation and the SECURE rules). For people reaching RMD age under current rules, the first RMD is due by April 1 of the year after you turn the applicable age (commonly 73 for many cohorts), with subsequent RMDs due by December 31 annually; delaying the first RMD can force two RMDs in one calendar year and increase taxable income in that year [6] [5] [8]. Available sources do not mention a comprehensive table of birth‑year cohorts beyond examples, but providers and the IRS tie exact divisors to the owner’s age in the distribution year [9] [2].
4. Inherited accounts — the “minus‑1” method and changing factors
For many non‑spouse designated beneficiaries the Single Life table is used and, after the initial year, providers subtract 1.0 from the life‑expectancy factor each year (the “minus‑1” approach), which shortens the divisor over time and increases annual RMDs as the beneficiary ages [10] [11]. Industry writeups note this produces a steadily rising withdrawal rate and can substantially change cashflow planning for beneficiaries compared with the original owner’s schedule [12] [11].
5. Hidden levers and policy shifts that affect retirees
Two less obvious drivers: legislative and IRS guidance changes (e.g., SECURE Act timing and subsequent IRS table interpretations) alter RMD starting ages and how tables apply; practitioners reported retrospective adjustments and IRS waivers that affected factors for several years, creating planning complexity [12] [13]. Beneficiary designation details — whether a spouse is sole primary beneficiary for the whole distribution year or whether contingent beneficiaries exist — can force different tables and therefore different RMDs [1] [3].
6. Practical impact — what retirees born in different years should expect
Retirees born in different years face different RMD start dates and thus different age‑based divisors; once you’re subject to RMDs you must recalculate annually because the divisor declines with age and will make the RMD larger each year [7] [9]. Those married to much‑younger spouses can expect lower annual RMDs if the Joint Life table applies; inherited‑IRA beneficiaries should expect faster depletion under the Single Life table and the minus‑1 method [4] [10].
7. What the reporting leaves out and what to do next
Available sources explain the mechanics and examples but do not provide a single, up‑to‑date birth‑year‑to‑first‑RMD table in this package — consult Publication 590‑B and plan providers for the exact divisor tied to your age and beneficiary situation [2] [14]. Given the tax consequences of timing the first RMD and the potential gap between owner and beneficiary rules, retirees should verify which table applies to each account, confirm beneficiary designations, and run year‑by‑year projections or get professional advice [5] [14].