The municipal ladder rested on 6.82 basis points of margin. North Carolina takes 17.99.

This article first appeared in The Nest Egg, my daily email, on 2026-10-09. 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. A split tape, the Nasdaq 100 down 1.39% while the Dow finished higher. Then the question this letter has been avoiding for three weeks without knowing it.

In today's issue

The tape. A 1.49-point spread between two indexes in one session, and yields lower across the curve. Two minutes.

$2,856.84. What the ladder has been paying North Carolina every year, in no letter so far. Four minutes.

11.64 basis points. The correction. The ladder misses the couple's bar and clears the survivor's. Six minutes.

One more thing. Three islands that are exempt, and the piece of paper that decides the whole thing. Two minutes.

The tape

Close of October 8, 2026, from CNBC US Markets, pulled at 4:15pm ET. Index levels and percentage changes are CNBC's own. Gold is the December 2026 contract and WTI the November 2026 contract. Gold, crude and both Treasury yields keep trading after the equity close, so each of those four changes is measured against the level this page printed yesterday rather than against an exchange settle.

Two indexes, one session, and 1.49 points between them. The Nasdaq 100 fell 1.39% while the Dow industrials rose 0.10% and the Russell 2000 finished flat at plus 0.03%. That is not a selloff, it is a rotation, and the VIX agreed by rising only 2.19% to 15.41 on a day the largest index fell more than a percent. Crude added 2.03% to $90.79 on the November contract, which expires on October 20, and gold rose 0.70% to $4,159.40. Yields fell across the curve: the 10-year down 5.9 basis points to 5.227% and the 30-year down 6.8 to 5.601%. For a household holding a long municipal ladder, that last line is the only one on the page that touched their balance sheet.

The story

On September 21 this letter looked at swapping a $1,600,000 taxable ladder into municipal bonds and found the household $14,651.80 a year poorer for it. On September 29 it corrected the yield, sized the ladder at $1,587,583.15, and showed the trade clearing its break-even after all. The $71,600 that ladder produces is what keeps the survivor under the $109,000 Medicare line. Every letter since has rested on it.

In none of them did anyone ask what North Carolina does with the interest.

North Carolina adds it back. The ladder has been paying state tax the whole time.

The position

$1,587,583.15 of municipal bonds yielding 4.51%, which is the average yield to maturity iShares published for its national municipal bond ETF on September 25. That produces $71,600.00 a year, and the ladder was sized to that number rather than to a round dollar amount because $71,600 is what keeps the survivor under the $109,000 Medicare line.

The break-evens from September 29, against a 5.13% taxable Treasury ladder of matched duration: the couple needs 4.4418%, the survivor alone needs 4.1243%. At 4.51% the ladder cleared both. That was the conclusion, and it was federal only.

The arithmetic

Step one. The rule, from the state's own page.

From the North Carolina Department of Revenue, Individual Income Tax, Filing Topics, Interest Income, read yesterday:

"All taxpayers who received interest on notes and bonds from states other than North Carolina must add this interest income to the North Carolina return because this interest income has not been included on your federal return."

It names the line: Form D-400 Schedule S, Part A, Additions to Federal Adjusted Gross Income.

Step two. What that costs, per year.

$71,600.00 at 3.99% is $2,856.84 a year. The ladder's yield to this household is not 4.51%. It is 4.3301%, which is 17.99 basis points lower.

Compounded for twenty years at the 3.90% after-tax reinvestment rate this letter has used all month, that is $84,193.92 of state tax on an asset this letter has called tax-exempt since September 21.

Step three. The part that actually breaks the trade.

Losing 17.99 basis points would be survivable if the margin were wide. It is not. The couple's break-even was 4.4418% against an actual 4.51%, so the entire municipal position was built on 6.82 basis points of margin. The state costs 2.64 times that.

And it gets worse, because the state does not treat the two sides alike. The same NCDOR page, on the taxable alternative:

"A taxpayer may take a deduction on the North Carolina income tax return for interest received from direct obligations of the United States to the extent this interest has already been included in federal taxable income or adjusted gross income as appropriate. The State does not tax this income."

So Treasuries pay no North Carolina tax at all, and out-of-state municipal bonds pay the full 3.99%. The comparison that was symmetric federally is lopsided at the state line, and it leans the wrong way.

Step four. So the bar rises while the yield stands still.

If the taxable side keeps all of its yield in North Carolina and the municipal side keeps 96.01% of its own, then the municipal yield has to be higher by the reciprocal of that figure to tie.

Couple: 4.4418% divided by 0.9601 is 4.6264%. Survivor: 4.1243% divided by 0.9601 is 4.2957%.

Break-evens are the municipal yields that leave this household even against a 5.13% taxable Treasury ladder of matched duration, carried from the September 29 issue. The North Carolina versions divide each by 0.9601, because the state adds back out-of-state municipal interest at 3.99% and deducts Treasury interest entirely. NCDOR, Interest Income, read October 8, 2026.

Step five. The correction.

At 4.51%, the ladder is 11.64 basis points short of the couple's bar and 21.43 clear of the survivor's.

September 29 said the swap worked for both. It works for one. While both are alive, this household would be better off in the Treasury ladder it sold.

In dollars: the corrected couple's bar requires $73,447.84 of income on this ladder. It produces $71,600.00. The gap is $1,847.84 a year, which compounds to $54,457.60 over twenty years at 3.90%.

A position that fixes itself at the worst possible moment

Look at what those four lines actually say. The ladder is wrong today and right at first death.

The reason is the one this letter has repeated since the middle of September. The survivor's bar is lower because the survivor's taxable alternative is worse: single brackets, a smaller standard deduction, and a Medicare threshold at half the joint one. Everything that makes widowhood expensive also makes tax-exempt income more valuable, and the municipal ladder is priced for the second condition while the household is still living in the first.

That is not an argument for holding a position that misses its bar by 11.64 basis points for however many years the couple has left. It is an argument for noticing that the holding is a bet on a date, and that nobody chose it that way.

What the four of them would say

The portfolio manager. Six point eight two basis points. That was the whole margin, and it survived three weeks of letters because the arithmetic was right and the question was incomplete. When a position clears its hurdle by less than ten basis points, the honest description is not that it clears. It is that you have not found the thing that will move it yet. A margin that thin is a research finding about your own ignorance, not an answer.

The CPA. Yesterday the state rate cancelled, because it fell on both sides of the comparison. Today it does not cancel at all, because it falls on one side only. Same state, same rate, opposite behaviour, and the difference is entirely in what the other asset is. That is the whole lesson about state tax: it is never a property of the asset you are looking at. It is a property of the pair.

The financial planner. The fix is not exotic. North Carolina deducts interest on its own bonds, so an in-state ladder pays the state nothing and only has to clear the original 4.4418%. Against the national fund it can give up as much as 17.99 basis points of yield and still leave this household ahead. The cost is concentration, a single state's credit instead of fifty, and that is a real trade rather than a free one. It is also the trade most people in this state should at least have been shown.

The estate attorney. And note which of these two people the position is built for. The ladder serves the survivor. The couple is carrying it. If the goal was the survivor's Medicare threshold all along, then say so in the investment policy statement, because an asset held for a contingency should be written down as one. Otherwise the next person to read this portfolio will mark it as a mistake and sell it the year before it starts working.

One more thing

Two more lines on that page, and one of them is larger than everything above.

The first is a carve-out. Verbatim: "Notes and bonds issued by Guam, Puerto Rico and the US Virgin Islands are not subject to this adjustment." Territorial bonds are exempt federally and exempt in North Carolina without being North Carolina paper. For a household in this position that is the only way to hold out-of-state issuers and pay no state tax.

The second is the one that should worry them. Verbatim: "Unless you have a supporting statement from the mutual fund showing it is not taxable to North Carolina you must add back all interest income which was exempt on your federal return."

Read that again. The default is all of it. The 4.51% in this letter came from a national municipal bond ETF, and a national fund holds some North Carolina paper. Without the fund's own state breakdown in hand, the exemption on that North Carolina slice is forfeited too, not because the bonds are wrong but because the paperwork is missing.

Everything above assumed the household has that statement. If they do not, the $2,856.84 is a floor rather than a figure.

Monday

There are now three candidate ladders on the table and no page that holds all three.

National municipal bonds, taxed by North Carolina. North Carolina municipal bonds, taxed by nobody. United States Treasuries, taxed federally and deducted by the state. Each one needs a different size to produce the $71,600 the survivor's Medicare threshold requires, each one puts a different number into that threshold, and this letter has never shown them beside each other.

Monday we rank all three on one page, after federal tax, after state tax, and after the surcharge, which is the first time this month those three layers have appeared in the same table.