RMD Age 73 vs 75: Born 1951-1959 vs 1960+ Cohort Math

SECURE 2.0 Act §107 changed the required minimum distribution age in a way that splits the population by birth year. If you were born December 1959, your first RMD is at age 73 — the same as everyone born in 1951 through 1959. If you were born January 1960 — just one calendar month later — your first RMD is at age 75, two years later. The cliff is not gradual. The same $1M traditional 401(k) balance produces materially different tax outcomes depending on which cohort you fall in, simply because of when your first mandatory distribution begins.

For the 1960+ cohort, the two extra years of deferral matter in three concrete ways: more Roth conversion capacity in the gap, more tax-deferred compounding on the pre-RMD balance, and a smaller initial RMD because of a slightly different divisor table. The 1951-1959 cohort gets none of these benefits — their planning window is two years shorter, their lifetime RMDs slightly larger, and their flexibility around the inheritance rules under IRC §401(a)(9)(H) somewhat narrower. This article walks through the exact cohort math.

The SECURE 2.0 RMD age schedule by birth year

The current RMD ages under SECURE 2.0 §107:

• Born before 1951: original 70½ (if started) or 72 under prior law. Already taking RMDs.
• Born 1951 - 1959: first RMD age = 73.
• Born 1960 or later: first RMD age = 75.

The schedule was intentionally drafted with a sharp cohort split rather than a phase-in. SECURE 2.0 was signed in late 2022 and the §107 provisions took effect immediately. The earliest 1960-cohort members (born January 1960) turn 65 in 2025, 73 in 2033, and 75 in 2035 — that 2035 date is when the first 1960-cohort RMDs hit IRS systems.

What the two-year deferral changes for the 1960+ cohort

1. Two more years of Roth conversion capacity

The gap years between retirement (typically 62-65) and first RMD are the highest-leverage tax window in retirement planning. During this gap, your taxable income is low (no SS yet if delayed, no RMDs yet), and you can fill the 12% and 22% federal brackets with Roth conversions at low effective rates.

The 1951-1959 cohort retiring at 65 has 8 gap years: ages 65, 66, 67, 68, 69, 70, 71, 72 — with the first RMD hitting at 73.

The 1960+ cohort retiring at 65 has 10 gap years: ages 65 through 74 — with the first RMD hitting at 75.

At an average $40K-$60K conversion per year (typical for a single retiree below the $103K IRMAA threshold), the 2 extra years add $80K-$120K of converted balance. Across a 20-year post-conversion retirement, those additional dollars compound tax-free in the Roth, producing $25K-$45K of additional ending Roth wealth.

2. Two more years of pre-RMD compounding

Every year you don't take an RMD is a year the full balance stays invested tax-deferred. The 1960+ cohort gets 2 extra years of compounding on the pre-RMD balance.

On a $1M starting balance at retirement age 65 with 6% net returns and no contributions or withdrawals:

• Balance at age 73 (RMD start for 1951-1959 cohort): $1M × 1.06^8 = $1.59M.
• Balance at age 75 (RMD start for 1960+ cohort): $1M × 1.06^10 = $1.79M.

The 1960+ cohort enters their first RMD year with $200K more in the account from compounding alone. Even after the larger initial RMD (because the divisor is slightly smaller at 75 than 73), the 1960+ cohort retains a meaningfully larger residual balance heading into their 80s.

3. Different first-RMD divisors

The Uniform Lifetime Table (IRS Pub. 590-B, Table III) provides RMD divisors that vary by age:

• Age 73: divisor 26.5 (= 3.77% of prior-year-end balance must be distributed)
• Age 74: divisor 25.5 (= 3.92%)
• Age 75: divisor 24.6 (= 4.07%)
• Age 76: divisor 23.7 (= 4.22%)
• Age 77: divisor 22.9 (= 4.37%)
• Age 80: divisor 20.2 (= 4.95%)
• Age 85: divisor 16.0 (= 6.25%)
• Age 90: divisor 12.2 (= 8.20%)

The 1951-1959 cohort starts RMDs at age 73 (divisor 26.5, 3.77% of balance). The 1960+ cohort starts at age 75 (divisor 24.6, 4.07% of balance). The 1960+ cohort never takes age-73 or age-74 RMDs at all.

Worked comparison: identical $1M balances, two cohorts

Take two retirees, both with $1M in a traditional IRA at retirement age 65 in 2026. Both delay SS to 70, take $40K/year from a taxable brokerage during the gap years, no other income. Both execute aggressive Roth conversions targeting the IRMAA threshold ($103K MAGI, after subtracting other income).

Cohort A: born 1958, first RMD at 73 (2034)

Gap years: 65-72 (8 years). Annual conversion capacity below IRMAA: roughly $80K-$90K in the early years (before SS), dropping to roughly $50K once SS at 70 stacks on. Total converted: ~8 years × $65K average = $520,000.

Traditional IRA balance at age 73: $1M started, grew 8 years at 6% minus conversions and brokerage uses = approximately $650,000. First-year RMD at 73: $650,000 / 26.5 = $24,528.

Years 73-95 (22 years of RMDs): cumulative ordinary income from RMDs at average 22% marginal rate = approximately $155,000 in federal tax.

Cohort B: born 1961, first RMD at 75 (2036)

Gap years: 65-74 (10 years). Same conversion capacity per year. Total converted: ~10 years × $65K average = $650,000. That's $130K more converted than Cohort A.

Traditional IRA balance at age 75: $1M started, grew 10 years at 6% minus larger conversions = approximately $580,000. First-year RMD at 75: $580,000 / 24.6 = $23,577.

Years 75-95 (20 years of RMDs): cumulative ordinary income from RMDs at average 22% marginal rate = approximately $130,000 in federal tax.

Cohort B advantage

More converted: $130K more in Roth, growing tax-free. At a 20-year compounding horizon and 6% returns, that compounds to roughly $230K of additional Roth wealth at age 95.

Less RMD tax over lifetime: $155K - $130K = $25K less federal tax.

Plus IRMAA savings: 2 fewer years of large RMD pushing MAGI above thresholds — rough estimate $2K-$4K in IRMAA avoided.

Total lifetime advantage of being in the 1960+ cohort vs 1951-1959 cohort on the same $1M starting balance: approximately $50K-$70K in federal tax savings and additional Roth wealth.

The inheritance interaction under IRC §401(a)(9)(H)

The 10-year rule for inherited IRAs interacts with the RMD age cohort in a way many planners miss. Under the IRS's 2024 final regulations:

• If the decedent had already started RMDs at the time of death: non-eligible designated beneficiaries (typically adult children) must take annual RMDs in years 1-9 AND fully distribute the account by year 10.
• If the decedent died before reaching their required beginning date: beneficiaries can defer all distributions to year 10, taking everything in the final year if desired.

The cohort distinction matters because the "required beginning date" depends on the RMD age. A retiree born 1959 has a required beginning date of April 1 in the year after they turn 73. A retiree born 1960 has a required beginning date of April 1 in the year after they turn 75.

Example: a retiree dies at age 74. If born 1959, their required beginning date was already past (April 1 after age 73). Their beneficiaries are subject to the annual-RMD-in-years-1-through-9 rule. If born 1960, their required beginning date was NOT yet past (would have been April 1 after age 75). Their beneficiaries can defer all distributions to year 10 — flexibility worth tens of thousands of dollars in bracket management for adult children inheriting at peak career-earnings.

The position: if you're born 1960+, design your conversion plan around 10 gap years, not 8

From MoneyMap US Position 3: "Most retirees with $1M+ in pre-tax accounts who retire before SS / RMDs should aggressively Roth-convert in the gap years — typically 60-73. This is the single most underused strategy in retirement planning."

For the 1960+ cohort, update the framing: "60-75, not 60-73." The 1960+ cohort's gap-year window is 10-15 years long, not 8-13. That's 25%+ more conversion runway. The annual target sizing doesn't change (still capped by IRMAA at $103K single MAGI), but the number of conversion years does — and so does the cumulative lifetime conversion total.

Concretely: if you were born 1960 or later, build your retirement-income plan assuming RMDs at 75. Don't accidentally model the 1951-1959 rules; older retirement-planning content often references age 73 as a fixed RMD age and is now incorrect for anyone born 1960+.

Where the cohort advantage doesn't matter much

• Small traditional balance (<$300K): lifetime RMDs are small enough that the cohort tax difference is $5K-$10K, not $50K-$70K. The planning win is modest.
• High charitable intent: if you plan to use QCDs (qualified charitable distributions under IRC §408(d)(8), available starting at age 70½) to satisfy RMDs entirely, your taxable RMD income approaches zero regardless of cohort. The age difference matters less.
• Required pre-RMD withdrawals: if your spending needs already force you to draw $40K+/year from the traditional IRA in your late 60s and early 70s, you're effectively "self-RMD-ing" before the mandatory age. The cohort distinction is moot — you would withdraw at similar rates either way.
• Roth-heavy retirement: if most of your retirement wealth is already in Roth (because you accumulated in Roth 401(k) or executed early-career backdoor Roths), there's little traditional balance to RMD against. The cohort difference doesn't matter.

Year-of-birth edge cases

• Born in 1959: you are squarely in the 1951-1959 cohort. First RMD at 73, year 2032. No ambiguity.
• Born in 1960: you are squarely in the 1960+ cohort. First RMD at 75, year 2035.
• Born early in 1960 (the boundary year): still 1960+ cohort. IRS uses the year of birth, not the date within the year.
• Born late in 1959 (the boundary year): still 1951-1959 cohort. The one-day difference between Dec 1959 and Jan 1960 produces a 2-year RMD-age difference. A clean cliff at the calendar boundary.
• RMD rules for inherited accounts are governed separately under IRC §401(a)(9)(H) and the 10-year rule — the birth-year cohort of the deceased determines the inherited IRA distribution requirements for the beneficiary, not the beneficiary's own birth year.

The legislative outlook

SECURE 2.0 §107 also includes a future RMD age increase to 75, originally scheduled for 2033. Under current law, the 1960+ cohort already gets the 75 age. The provision is fully phased in — no further legislative actions are needed to lock in the 1960+ benefit. SECURE 3.0 has been discussed in Congress but no specific RMD-age changes have advanced as of mid-2026.

Future legislation could conceivably reverse the cohort split or move all retirees to a single age. As of this writing the 75 age for 1960+ is settled law. Plan around it.

What to do next

1. Confirm your birth year and identify your cohort: 1951-1959 (first RMD at 73) vs 1960+ (first RMD at 75).
2. If 1960+: build your Roth conversion plan around 10 gap years, not 8. The annual sizing target (cap at IRMAA threshold) doesn't change, but the number of conversion years does.
3. If 1951-1959 and approaching retirement: maximize each gap year's conversion. You have fewer years of opportunity than younger cohorts; compress more conversion into each one.
4. For estate planning: factor the cohort into beneficiary planning under IRC §401(a)(9)(H). Adult-child beneficiaries inheriting from a 1960+ decedent who dies before age 75 have more distribution flexibility than those inheriting from a 1951-1959 decedent who dies after age 73.
5. Don't rely on older retirement-planning content. Anything written before SECURE 2.0 (Dec 2022) or that references a uniform age-73 RMD start without the cohort split is partially obsolete.

Key takeaways

• Under SECURE 2.0 §107, RMDs start at 73 for those born 1951-1959 and at 75 for those born 1960+. The split is cliff-based by year of birth, with no proration.
• The 1960+ cohort gets 2 extra gap years (10 vs 8 for retirees at 65). At $40K-$60K of conversion per year, this represents $80K-$120K of additional Roth conversion capacity.
• The 1960+ cohort enters their first RMD year with approximately $200K more in compounded balance on a $1M starting position (10 years of 6% compounding vs 8 years).
• RMD divisors at age 73 (26.5) and 75 (24.6) produce slightly different first-year percentages. The 1960+ cohort skips the age-73 and 74 RMDs entirely — on a $1M balance, roughly $70K of deferred ordinary income.
• Lifetime tax savings for the 1960+ cohort vs 1951-1959 cohort on identical $1M balances: approximately $50K-$70K in combined federal tax savings, IRMAA avoidance, and additional Roth-compounded wealth.
• The 10-year inherited IRA rule under IRC §401(a)(9)(H) interacts with the cohort split: beneficiaries of a 1960+ decedent who dies before age 75 have more distribution flexibility than those inheriting from a 1951-1959 decedent who has already started RMDs.
• If you were born 1960 or later, design your conversion plan around 10 gap years, not 8. Older retirement-planning content referencing a uniform age-73 RMD start is partially obsolete.