Roth Conversion at 63 vs Waiting for RMDs at 73: How a $1.5M IRA Creates a $140,000 Avoidable Tax Bill
Roth Conversion at 63 vs Waiting for RMDs at 73: How a $1.5M IRA Creates a $140,000 Avoidable Tax Bill
You retire at 63 with $1.5 million sitting in a traditional IRA. No required distributions yet. Social Security hasn't started. Your income is suddenly the lowest it's been in decades.
Most people see that as relief. Smart retirement planners see it as the most valuable tax window of your life — and one that quietly closes when you turn 73.
Here's the scenario I want to walk through: if you do nothing with that IRA between 63 and 73, you'll face a forced withdrawal schedule at 73 that could push you into a higher tax bracket, trigger Medicare premium surcharges you didn't anticipate, and make up to 85% of your Social Security benefit taxable. The IRS doesn't ask permission.
But if you run a deliberate Roth conversion strategy during that decade — filling your tax bracket each year at 22% instead of 32% later — the math shows you can avoid a six-figure tax liability while simultaneously building a tax-free income source your heirs will thank you for.
Let's build the numbers.
The RMD Bomb: What Your $1.5M IRA Looks Like at 73
Under SECURE 2.0, required minimum distributions now begin at age 73 (bumped from 72). If your IRA earns a conservative 6% annually and you make no withdrawals during the decade between 63 and 73, that $1.5 million becomes:
$1.5M × (1.06)^10 = approximately $2.69 million
Your first RMD, calculated using the IRS Uniform Lifetime Table (divisor of 26.5 at age 73):
$2,686,000 ÷ 26.5 = ~$101,400 required withdrawal in year one
Now layer on Social Security. If you claim at 70 and receive $3,200/month — a realistic benefit for a high-earner — that's $38,400/year. With combined income above the IRS provisional income thresholds, up to 85% of your Social Security is taxable, adding another ~$32,600 in taxable income.
Your total gross income in year one: roughly $134,000. After the standard deduction ($32,300 for married filing jointly in 2025), you're looking at $101,700 in taxable income — solidly in the 22% bracket, pushing into 24%.
But here's the compounding problem: your RMD grows every year as your account grows faster than you can withdraw it. By age 78, your divisor shrinks to 22.0 while your remaining balance may still exceed $2.4 million. Your RMD at 78 could be $109,000+. You're not solving this problem — you're feeding it.
The Roth Conversion Window: Age 63–72
The decade before RMDs begin is the only time you get to choose your tax rate on this money. Between 63 and 72, you control the withdrawal — the IRS doesn't.
The strategy: Convert $75,000 per year from your traditional IRA to a Roth IRA across 10 years.
Total converted: $750,000 Approximate tax paid (at 22% effective rate on conversions, assuming modest other income): ~$165,000 over 10 years
What does your IRA look like at 73 after these conversions?
With annual conversions reducing the IRA balance each year, and assuming 6% growth on the remaining balance, the ending IRA balance at 73 drops to approximately $1.71 million (compared to $2.69M without conversions).
New first-year RMD: $1,710,000 ÷ 26.5 = ~$64,500
That's $36,900 less in forced taxable income in year one alone. At a 24% marginal rate — where many retirees land by age 75 — that's $8,856 in annual tax savings, every single year, for as long as the RMDs continue.
Over a 20-year RMD period, the tax savings on reduced RMDs alone approximate $177,000 (nominal, not NPV-adjusted). You paid $165,000 during conversions at 22%. You avoid $177,000+ in taxes later at 24%–32%.
Net benefit: roughly $12,000–$75,000 depending on how far into the higher brackets your unconverted RMDs would have pushed you.
This is why I always say the Roth conversion decision isn't about your tax rate today — it's about your tax rate in year 12 of retirement when your RMD, Social Security, and any investment income are all stacking simultaneously.
You can model this for your specific situation at Lontevis — the tool runs the conversion ladder against your actual bracket, not a generic one.
IRMAA: The Tax Nobody Talks About Until It Hits
Here's the number that catches most retirees off guard: if your modified adjusted gross income (MAGI) exceeds $212,000 as a married couple in 2025, your Medicare Part B premiums jump from $185/month to $259/month per person. That's an extra $888/year per person — $1,776/year as a couple — just from crossing an income threshold.
The second IRMAA tier kicks in above $266,000 MAGI, adding another layer. The surcharges are retroactive based on your income two years prior, which means the $101,400 RMD you took at 73 shows up in your Medicare premium calculation at 75.
The Roth conversion strategy above isn't just about income taxes. It's also about keeping MAGI below IRMAA thresholds during the high-income RMD years.
For a deeper look at how IRMAA interacts with IRA conversion amounts, see our analysis of Roth Conversion at 63: How Converting $80,000/Year From a $2M IRA Avoids IRMAA Surcharges and Saves $140,000 in Retirement Taxes.
Capital Gains Harvesting: The Other Opportunity in Low-Income Years
If your $1.5M IRA sits alongside a taxable brokerage account — say, $400,000 in appreciated stock — the same low-income years between 63 and 72 offer a second tax optimization: 0% long-term capital gains harvesting.
In 2025, married filers pay 0% on long-term capital gains up to $94,050 in taxable income. If your only income in a given year is $40,000 in Roth conversions (below your standard deduction), you may be able to realize another $50,000+ in capital gains at zero federal tax.
Compare that to realizing those same gains at 73, when your RMDs have already consumed your 0% bracket. Those gains would then be taxed at 15% or even 20%.
On $50,000 in capital gains, the difference between 0% and 15% is $7,500 per year. Spread across 5–7 years of strategic harvesting, that's another $37,500–$52,500 in tax savings — without touching your Roth conversion math.
| Strategy | Action Window | Savings per Year | Total Over Period |
|---|---|---|---|
| Roth Conversions ($75K/yr) | Age 63–72 | ~$8,856/yr on reduced RMDs | ~$177,000+ |
| Capital Gains Harvesting | Age 63–72 | ~$7,500–$10,000 | ~$37,500–$52,500 |
| IRMAA Avoidance | Age 73+ | ~$1,776–$4,200/yr | ~$25,000–$50,000+ |
| Combined Strategy | 63–73+ | — | $200,000–$280,000 |
This is the kind of multi-variable analysis Lontevis runs for you — layering Roth conversions, capital gains harvesting, and IRMAA thresholds simultaneously so you're optimizing the whole picture, not just one piece.
Why Social Security Uncertainty Makes This More Urgent, Not Less
The Social Security trust fund picture adds a layer of urgency to pre-retirement tax planning. The Social Security trustees currently project that the combined trust funds could face depletion around 2033–2035 if Congress takes no action, which the CNBC report on Social Security's trust fund noted could trigger automatic benefit reductions under current law — potentially up to a 21% cut.
I'm not going to tell you Social Security is going away. The political will to fully cut benefits simply doesn't exist. But I am going to point out what it means for your tax planning:
If your projected Social Security benefit faces any reduction — even a 10% cut — your break-even analysis on Roth conversions shifts in favor of converting more, sooner.
Here's why: Roth IRA assets grow tax-free and have no RMDs. If your guaranteed income (Social Security) turns out lower than projected, you'll be drawing more from your IRA — directly increasing taxable income in those years. The Roth acts as a buffer: tax-free withdrawals that don't push you into a higher bracket or trigger IRMAA regardless of what Congress does with Social Security between now and 2033.
The smart move isn't to panic about Social Security. It's to build a withdrawal structure robust enough to handle a range of Social Security outcomes — and Roth conversions are the most direct mechanism for that.
How to Think About the Conversion Amount Each Year
The $75,000/year conversion figure isn't arbitrary — it's designed to fill, but not overflow, the 22% bracket.
For a married couple filing jointly in 2025 with no other income except the conversion:
- Standard deduction: $32,300
- Top of the 22% bracket: $201,050 taxable income
- Effective conversion budget before entering 24%: up to $233,350 gross
If you're also receiving Social Security, doing part-time consulting, or earning dividends, your conversion budget shrinks accordingly. This is where most people leave money on the table — they either convert too little (leaving the bracket unfilled) or too much (accidentally jumping into 24% or 32%).
The right number varies every single year. Your income, account balance, bracket thresholds, and IRMAA levels all shift. A tool that recalculates this annually — rather than a static spreadsheet you built at 63 — makes a meaningful financial difference.
The Bottom Line on a $1.5M IRA
| Scenario | IRA Balance at 73 | First-Year RMD | Peak Marginal Rate | Est. Lifetime Tax Cost |
|---|---|---|---|---|
| No conversions (wait for RMDs) | ~$2.69M | ~$101,400 | 24–32% | High |
| $75K/year Roth conversions (63–72) | ~$1.71M | ~$64,500 | 22–24% | Significantly lower |
| Difference | — | ~$36,900 less forced income | — | ~$140,000–$200,000 saved |
These are estimates — your actual numbers depend on your starting balance, return assumptions, other income sources, state taxes, and filing status. The direction of the math, however, is consistent: the tax window between retirement and RMDs is real, and it closes quietly.
The tax resistance stories making headlines are about people withholding taxes illegally — an approach that ends in IRS penalties and interest. The legal version of resisting an oversized tax bill is called tax planning, and the decade between 63 and 73 is where most of the leverage lives.
Run your specific IRA balance, annual income, and Social Security estimate through the optimizer at Lontevis to find out what your Roth conversion budget looks like this year — and what the cumulative savings are across your retirement horizon. The math takes 60 seconds. The decision is worth a lot more than that.
Sources
- What could happen to Social Security benefits in six years if Congress doesn’t act? It depends, experts say — CNBC Personal Finance
- ‘Tax resistance’ gains attention amid ICE protests, Iran war — and IRS penalties could follow — CNBC Personal Finance
- These Hidden Mastercard Perks Could Upgrade Your Next Trip — NerdWallet Retirement
- Hyatt Regency Hill Country Resort Review: A Top-Value Texas Escape — NerdWallet Retirement
- 7 Best Online and Prepaid Legal Services for Small Businesses — NerdWallet Retirement