The same conversion costs $9,247 less in the year he dies.

This article first appeared in The Nest Egg, my daily email, on 2026-09-24. Read the original issue. It is educational, not a recommendation for you. The household in it is a hypothetical example, and market figures are as of the date shown and will have changed.

Every figure below names its document. Every calculation is shown. Nothing here is a forecast.

Good morning. Everything sold off yesterday, the Russell 2000 hardest at 1.77%, and the 10-year jumped 13.5 basis points to 5.102%. Then the year nobody plans for.

In today's issue

The tape. All four indexes lower, the VIX up 6.83%, and the 10-year back above 5.10%. Two minutes.

Zero. The household's federal income tax in the year he dies, before any conversion at all. Four minutes.

0, 18.5, 10, 12, 22. The rate on each slice of a conversion in that year, in that order. Three minutes.

One more thing. Why almost nobody captures this, and the one beneficiary who never can. One minute.

The tape

Closing levels and session changes, CNBC US markets, September 23, 2026. Gold and WTI crude are front-month futures settlements. The crude front month rolled from October to November, so its change is measured against the November contract's prior close and the level is not comparable with yesterday's.

The story

Every letter this week has priced a conversion while both spouses are alive. That is the normal assumption, and there is exactly one year where it is wrong.

When a married person dies, the surviving spouse generally files a joint return for that entire year. Joint brackets. The $35,500 joint standard deduction. The $218,000 joint Medicare line.

And the income is already a survivor's income. His Social Security stopped. Hers continues at the larger of the two benefits.

One year with a widow's income and a couple's tax table.

It is the cheapest tax year this household will ever have. It arrives without warning, and the deadline to use it is December 31.

The position

The same household, eighth day in a row. $1,600,000 in a municipal ladder paying $53,280 of tax-exempt interest. $1,200,000 in a traditional IRA. Both were 73, so neither had reached 75 and there is no year-of-death required distribution to take first.

He dies. She receives the $44,000 survivor benefit, and she files jointly for the year.

Provisional income: $53,280 plus half of $44,000, or $75,280. The joint thresholds are $32,000 and $44,000, so 85% of ($75,280 minus $44,000) is $26,588, plus the $6,000 joint adjustment. Taxable Social Security: $32,588.

Adjusted gross income: $32,588. The joint standard deduction is $35,500.

Taxable income: zero. Federal income tax: zero.

The arithmetic

Step one. The first $1,574.05 is free.

Her adjusted gross income sits $2,912 below the deduction. Each converted dollar raises taxable income by $1.85, because it drags $0.85 of Social Security along with it.

$2,912 divided by 1.85 is $1,574.05 of conversion before a single dollar becomes taxable.

Step two. The ladder.

$0 to $1,574.05: 0.00%, or $0. $1,574.05 to $5,661.18: 18.50%, or $756.12. That is the 10% bracket times 1.85. $5,661.18 to $22,900: 10.00%, or $1,723.88. Her benefit is now fully taxed, so the drag stops. $22,900 to $98,900: 12.00%, or $9,120.00. $98,900 to $166,465.31: 22.00%, or $14,864.37.

The rate goes 0, then 18.5, then back down to 10, then 12, then 22. Converting more money lowers her marginal rate for a stretch of $17,238.82, which is not how anyone expects a tax table to behave.

Step three. The cheapest conversion is the wrong one.

Filling the 12% bracket takes a conversion of $98,900. The tax is $11,600.00, a blended 11.73%, and their Medicare income that year is $189,580, comfortably under the $218,000 joint line. No surcharge at all.

That is the cheapest conversion in eight days of these letters, and it does not do the job.

At 5% growth for two years the IRA still arrives at $1,213,962.75. Her required distribution is $49,348.08 and her Medicare income is $140,028.08, which is past the $137,000 line and back in the $240.40 tier. All of it for nothing.

Step four. The conversion that works.

The target is Wednesday's: get the IRA to $1,139,472 by her first distribution year, which takes $166,465.31.

In the year of death, taxable income is $168,365.31 and the tax is $26,464.37, an effective rate of 15.90%.

Their Medicare income is $257,145.31. That is past the $218,000 joint line but under $274,000, so it is the first tier. And only one person is left to pay a premium: $95.70 a month, or $1,148.40.

Total: $27,612.77.

Wednesday, with both alive, the same conversion cost $31,090.57 of tax at 18.68%, plus $5,769.60 of surcharge, because their income crossed $274,000 and two people paid it. Total $36,860.17.

Same conversion. Same outcome for her. $9,247.40 less.

Step five. The payback.

Her saving is identical either way, $3,377.71 a year. $27,612.77 divided by $3,377.71 is 8.18 years, against 10.91.

2026 rates per Revenue Procedure 2025-32 and the 2026 CMS income-related monthly adjustment amounts. Both conversions are sized to bring the IRA to $1,139,472 in her first distribution year at 5% growth. Growth rates are assumptions used to test sensitivity, not expectations. Hypothetical illustration of published rates, built to show arithmetic. Not a projection of any reader's result and not a recommendation.

What the four of them would say

The portfolio manager. Nothing in the portfolio changed today. Same ladder, same IRA, same conversion, same result for her. The entire $9,247.40 came from the calendar.

The CPA. The year of death is the most consequential return this household will ever file, and it is filed by someone who has just been widowed, usually by a preparer who was never told the date mattered. The conversion has to happen inside that calendar year. Not during the estate administration, not while the return is being prepared in April. By the time most people open the file, the year is over.

The financial planner. Look at the two answers pointing in opposite directions. The cheapest conversion is $98,900 at 11.73% with no surcharge. The right conversion is $166,465.31 at 15.90% with one. The second costs $16,012.77 more and is the only one that clears her Medicare line for the rest of her life. Cheapest and correct are different words.

The estate attorney. None of this exists until the account is retitled. A surviving spouse may treat the inherited IRA as her own, and only then can she convert it. A non-spouse beneficiary cannot convert an inherited IRA at all, under any circumstance. So this letter describes one beneficiary, one year, and a piece of paperwork that has to come first.

One more thing

Three things have to line up for a household to capture this, and they compound.

The deadline is December 31 of the year of death, not the filing deadline in April. A conversion in January is a single filer's conversion, at single brackets, against a single standard deduction.

The account has to be retitled first. Spouse only, and it has to be done inside the same window.

The right size is not the cheap-looking size. $98,900 feels responsible and accomplishes nothing. $166,465.31 costs $16,012.77 more and is the answer.

A widow has roughly four months, a retitling, and a counterintuitive number to get right, in the worst season of her life. That is the real reason this window is almost never used, and it has nothing to do with the arithmetic.

Tomorrow

Eight letters, one household, and a great many numbers. Tomorrow we put every decision from the week on one page and rank them by what each one actually changed, in dollars. Two of them turn out not to matter at all.

Sources

2026 brackets, standard deduction and the additional deduction at 65 or older: Revenue Procedure 2025-32. Taxation of Social Security benefits: 26 U.S.C. 86. Roth conversions, qualified distributions and inherited accounts: 26 U.S.C. 408A. Spousal treatment of an inherited IRA and Uniform Lifetime Table divisors: IRS Publication 590-B. 2026 Part B and Part D income-related monthly adjustment amounts and their two-year lookback: Centers for Medicare & Medicaid Services. The Medicare surcharge income definition: 42 U.S.C. 1395r(i)(4). Joint return for the year of a spouse's death: 26 U.S.C. 6013. Market levels, close of September 23, 2026: CNBC US markets.

The conversation a portfolio manager, a CPA, a financial planner and an estate attorney would have about your money if the four of them were ever in the same room. None of them ever talk to each other. This is that room, every weekday at 6:45am, sized to a portfolio between $500,000 and $5,000,000.

The Nest Egg is educational material published by a registered representative. It is not tax, legal or investment advice, and it is not an offer or solicitation. Every case shown is a hypothetical illustration of published rates, built to demonstrate arithmetic, and is not a projection of any reader's result. Growth rates shown are assumptions used to test sensitivity, not expectations. State taxes, itemized deductions and the character of investment income are not modeled here and change the result. Nothing here is a recommendation of any security. Consult your own tax and legal advisors before acting.