Required Beginning Date and Final Withdrawal Math

The IRS does not care whether you need the money. Once you reach 73, IRC Section 401(a)(9) requires you to withdraw a minimum amount from every traditional IRA and 401(k) you own, every single year, until the account is empty or you die — whichever comes first. The amount starts at roughly 3.77% of your balance and climbs each year as the Uniform Lifetime Table divisor shrinks. By age 90, you are withdrawing over 10% annually. By age 100, over 15%. The math is mechanical, but the tax consequences are not: each RMD stacks on top of Social Security, pension income, and any other ordinary income, and the combined total determines your marginal tax rate, how much of your Social Security is taxable (up to 85%), and whether you pay IRMAA surcharges on Medicare premiums.

The required beginning date: April 1 rule explained

Under SECURE 2.0, the required beginning date depends on your birth year. If you were born between 1951 and 1959, your RMD trigger age is 73. If you were born in 1960 or later, the trigger age is 75 (effective 2033). The required beginning date itself is April 1 of the year after you reach the trigger age. Turn 73 in 2026, and your required beginning date is April 1, 2027.

This April 1 grace period for the first RMD is a trap, not a gift. If you defer your first RMD to early 2027, you still owe a second RMD for 2027 by December 31, 2027. That is two full RMDs in one calendar year — potentially $60,000 to $80,000 of additional taxable income that pushes you into a higher bracket and above IRMAA thresholds. For every subsequent year, the deadline is simply December 31.

Accounts subject to RMDs: traditional IRAs, traditional 401(k)s, 403(b)s, 457(b) governmental plans, SEP IRAs, and SIMPLE IRAs. Accounts exempt from RMDs: Roth IRAs (during the original owner’s lifetime) and, as of 2024 under SECURE 2.0, designated Roth accounts inside 401(k) and 403(b) plans.

The Uniform Lifetime Table: how the divisor works

IRS Publication 590-B contains the Uniform Lifetime Table, which provides the life expectancy divisor for each age. You divide your December 31 prior-year account balance by this divisor to calculate your RMD. The table assumes a beneficiary 10 years younger than the account owner. If your sole beneficiary is a spouse more than 10 years younger, you use the Joint Life and Last Survivor Expectancy Table instead, which produces a larger divisor and a smaller RMD.

Notice the acceleration. At 73, you withdraw 3.77%. By 85, you withdraw 6.76% — nearly double. By 95, you withdraw 16.95%. The Uniform Lifetime Table is designed to deplete the account over the owner’s statistical remaining lifespan, but if your investments grow faster than the withdrawal rate in early years, the balance can actually increase — which means larger RMDs in later years, not smaller ones. This is the RMD growth trap: strong market returns in your 70s can produce unexpectedly large forced distributions in your 80s and 90s.

Worked example: Robert and Diane, ages 71 and 69

Robert is a retired project manager; Diane is a retired school administrator. They are two years away from Robert’s required beginning date. Their financial picture:

• Robert’s traditional IRA (rolled from 401(k)): $620,000
• Diane’s traditional IRA: $300,000
• Combined traditional balance: $920,000
• Roth IRAs: $85,000 combined
• Joint taxable brokerage: $140,000
• Social Security (already claiming at FRA): $78,000/year combined ($46,000 Robert, $32,000 Diane)
• Annual spending: $92,000
• Filing status: Married filing jointly

The two-year Roth conversion window (ages 71–72)

Robert and Diane have two years before RMDs begin. Their current taxable income is roughly $78,000 in Social Security (up to 85% taxable, so approximately $66,300 in taxable SS) plus $14,000 in portfolio withdrawals to cover the gap between Social Security and spending. Total taxable income before conversions: approximately $80,300 after the standard deduction of $32,300 (MFJ, 2026).

The 22% bracket for MFJ in 2026 runs from $94,300 to $190,750. They have room to convert roughly $110,000 per year ($190,750 − $80,300 = $110,450) and stay in the 22% bracket. But they also need to watch the IRMAA threshold at $206,000 MAGI. Adding the standard deduction back, their MAGI ceiling is approximately $206,000, and their current MAGI (before conversions) is roughly $80,300 + $32,300 = $112,600. That leaves $93,400 of Roth conversion headroom below the IRMAA cliff.

Conservative approach: Convert $90,000 per year for two years. Total converted: $180,000. Tax cost at approximately 22%: $39,600 per year, or $79,200 total. The traditional IRA balance at age 73 (assuming 5% growth and $180,000 removed): approximately $787,000 instead of $1,014,000.

RMD trajectory: with conversions vs. without

The Roth conversions reduce every future RMD by approximately 22%. The annual tax savings shown assume the avoided RMD income would have been taxed at the 22% marginal rate. Over 20 years of distributions (ages 73 to 92), the cumulative tax savings exceed $50,000 — more than recovering the $79,200 paid in conversion taxes, especially since the converted dollars continue growing tax-free inside the Roth.

How RMDs interact with Social Security taxation

Up to 85% of Social Security benefits become taxable when combined income (AGI + nontaxable interest + half of Social Security) exceeds $44,000 for married filing jointly. For Robert and Diane, their $78,000 in Social Security alone puts their provisional income at $39,000 (half of SS). Add a $30,000 RMD and provisional income jumps to $69,000 — well above the $44,000 threshold. Roughly $66,300 of their $78,000 Social Security benefit becomes taxable.

Every additional dollar of RMD income above the $44,000 threshold does not just add $1 of taxable income — it can also make an additional $0.85 of Social Security taxable. This creates an effective marginal rate that is higher than the statutory bracket rate. A retiree in the 22% bracket who triggers the Social Security taxation phase-in faces an effective marginal rate of approximately 40.7% (22% × 1.85) on RMD dollars in that range. This is the hidden tax cliff that makes pre-RMD Roth conversions so valuable.

IRMAA: the Medicare surcharge RMDs can trigger

Medicare Part B and Part D premiums increase when your modified adjusted gross income exceeds $103,000 (single) or $206,000 (married filing jointly), based on the tax return from two years prior. The IRMAA brackets in 2026:

For Robert and Diane, their MAGI at age 73 without conversions would be approximately $78,000 (Social Security) + $38,264 (RMD) + any taxable brokerage income. If they also took a capital gain of $15,000 from rebalancing, total MAGI reaches approximately $131,264 — well below the $206,000 MFJ threshold. But as RMDs grow in their 80s (potentially $55,000 to $67,000), the IRMAA risk increases, especially if the traditional IRA balance grows from strong market returns. Shrinking the traditional balance through early conversions is the primary defense.

The final-year withdrawal: what happens at death

When a traditional IRA owner dies, the RMD for the year of death must still be taken. If Robert dies at age 85 and has not yet taken his RMD for that year, Diane (as beneficiary) must withdraw Robert’s RMD by December 31 of the year of death. The amount is calculated using Robert’s age (85) and the corresponding Uniform Lifetime Table divisor (14.8).

After the year-of-death RMD is satisfied, Diane as the surviving spouse has three options for the remaining balance:

• Treat the IRA as her own. She rolls the balance into her own IRA. RMDs are recalculated using her age and the Uniform Lifetime Table. If she is younger than 73, no RMDs are required until she reaches that age.
• Remain as beneficiary. She takes distributions based on her own single life expectancy from the IRS Single Life Expectancy Table. This can be advantageous if she is younger than 59½ and needs penalty-free access.
• Elect the 10-year rule. Empty the account within 10 years. Rarely advantageous for a surviving spouse but available.

For non-spouse beneficiaries (children, siblings, trusts), the SECURE Act’s 10-year rule applies: the entire inherited IRA must be distributed by December 31 of the tenth year after the owner’s death. If the owner had already begun RMDs (was past the required beginning date), annual distributions within the 10-year window are also required — you cannot simply wait until year 10 to take everything.

Withdrawal sequencing: which account to draw from and when

The optimal withdrawal sequence for most retirees follows this general framework, adjusted year by year based on where you stand relative to tax bracket boundaries and IRMAA thresholds:

• Before the required beginning date (pre-73): Fund spending from taxable accounts first (favorable capital gains rates). Use the low-income years to convert traditional IRA dollars to Roth up to the IRMAA threshold. Every dollar converted now is a dollar that never generates a forced RMD.
• Ages 73–85 (active RMD phase): Take the RMD first — it is mandatory. If the RMD exceeds your spending need, reinvest the excess in a taxable brokerage account. If spending exceeds the RMD, draw the gap from taxable accounts. Avoid touching Roth accounts.
• Ages 85+ (accelerating RMDs): RMDs may now exceed annual spending needs. The excess becomes forced savings in taxable accounts. Qualified charitable distributions (QCDs) of up to $105,000 per year under IRC Section 408(d)(8) can satisfy part of the RMD without increasing AGI — a powerful tool for charitably inclined retirees in this phase.
• Roth accounts last: Roth IRAs should generally be the last accounts drawn. Every additional year of tax-free compounding increases their value, and they provide a tax-free reserve for large unexpected expenses (medical costs, long-term care) that would otherwise spike your taxable income.

Edge cases that change the math

Still working past 73: If you are still employed and participating in your current employer’s 401(k), you can delay RMDs from that specific plan (not from IRAs or prior employer plans) until April 1 of the year after you retire. This “still working” exception under IRC Section 401(a)(9)(C) does not apply to 5% or greater owners of the company.

Spouse more than 10 years younger: If your sole beneficiary is a spouse who is more than 10 years younger, you use the Joint Life and Last Survivor Expectancy Table instead of the Uniform Lifetime Table. This produces a larger divisor and smaller RMDs. A 75-year-old with a 60-year-old spouse has a joint divisor of approximately 26.2 versus 22.9 on the Uniform table — a 14% reduction in the RMD.

Multiple accounts: You calculate the RMD for each traditional IRA separately but can take the total from any one IRA or any combination. This flexibility lets you direct distributions from the IRA holding the asset you most want to liquidate. 401(k) plans do not aggregate — each plan’s RMD must come from that specific plan.

Key takeaways

• The required beginning date under SECURE 2.0 is April 1 of the year after you turn 73 (75 for those born 1960+). Deferring the first RMD to that April 1 deadline forces two distributions into one calendar year — a tax trap most retirees should avoid by taking the first RMD in the year they turn 73.
• RMDs are calculated by dividing the prior-year December 31 balance by the Uniform Lifetime Table divisor from IRS Publication 590-B. The withdrawal percentage starts at 3.77% at age 73 and accelerates to over 10% by age 90 and over 16% by age 95 — making large traditional IRA balances increasingly expensive to hold in later years.
• Roth conversions between retirement and the required beginning date are the primary tool for controlling lifetime RMD exposure. Every dollar converted to Roth under IRC Section 408A eliminates a future forced distribution, reduces the taxable share of Social Security, and avoids potential IRMAA surcharges. Size conversions to fill the current bracket without crossing the IRMAA threshold ($206,000 MAGI for MFJ in 2026).
• When the account owner dies, the RMD for the year of death must still be taken by the beneficiary. Surviving spouses can roll the balance into their own IRA. Non-spouse beneficiaries face the 10-year rule, with annual distributions required if the owner had passed the required beginning date.
• Withdrawal sequencing matters as much as the RMD math itself. Draw from taxable accounts first (pre-73), take mandatory RMDs and supplement from taxable accounts (73–85), use QCDs to offset accelerating RMDs (85+), and preserve Roth accounts for last — their tax-free compounding is most valuable the longer it continues.