Borrow at 5%, Earn 6% in X Money? The Box-Spread Carry Trade After Tax

“So who’s going to borrow at ~5% using a box-spread loan, park the proceeds in X Money earning 6% APY, and collect the ~1% spread? What could possibly go wrong?”

From my Engineer Investor account (@egr_investor) on X, November 5, 2026. Disclosure: I write both Summitward and the Engineer Investor account.

Both rates in that post are real. On November 2, 2026, SPX box spreads expiring in November 2027 traded at an implied 5.05%,¹ and X Money pays 6.00% APY to customers who meet its direct-deposit test.² Borrow $100,000 for a year at 5%, earn 6% on it, and the spread is $1,000 before tax.

After tax the answer runs from a gain of $592 to a loss of $1,448 on that $100,000. For a high earner whose other gains are long-term, it is negative. The two sides of the trade are taxed differently: the interest is ordinary income, and the box’s cost is a capital loss whose value depends on what else is on your return. Then there is a practical problem the arithmetic hides. The box must be repaid on a fixed date, and X Money’s default limit on withdrawals to a linked bank is $7,500 a month.³

The trade and the quotes behind it

A short box spread is four SPX options that together pay a fixed amount at expiration whatever the index does. Selling one raises cash today against that fixed obligation, which makes it a zero-coupon loan. Our box spread loans guide covers the mechanics, the rate conventions and the execution details. What matters here is the price. Box rates on November 2, 2026, by expiration:¹

Box rates: Boxtrades volume-weighted means, before commissions. Treasury: daily par yield curve, November 2, 2026.⁴

The one-year box sat about 67 basis points above the one-year Treasury. That is wide by historical standards. Researchers at the New York Fed found the one-year box rate averaged 35 basis points above Treasuries from January 1996 to April 2023, peaking near 130 basis points in October 2008.⁵ A St. Louis Fed analysis of 18-month boxes put the gap at 34 basis points on average in 2012 to 2019 and 9 in 2025 through August.⁶ The 5.05% figure rests on nine trades, so treat it as indicative. The shape of the curve is clear either way: shorter boxes cost less.

On the deposit side, X Money pays 4.00% APY as standard and 6.00% to subscribers of its Premium, Super or Ultra plans, or to anyone who receives at least $1,000 of qualifying deposits in a trailing 34 days. A qualifying deposit is an ACH credit with the PPD code that payroll uses, or an X creator payout.² The boost applies to the account balance as a whole. X’s own example: with $200,000 in the account, “$150,000 earns 6.00% APY and the other $50,000 earns 4.00% APY.”⁷ So a borrower whose paycheck already lands at X would earn 6% on borrowed money transferred in from a brokerage. Three more terms matter:

• From December 1, 2026, 6% applies only to the first $150,000. The rest earns 4%.
• The rate is “variable and subject to change at any time.” The account agreement adds that X may discontinue the interest feature entirely, and the terms can change without prior notice.³
• New York residents earn no interest. Existing New York accounts stopped earning it on October 1, 2026.⁷

Why would anyone pay 6% when the 13-week Treasury bill yielded 4.10% on November 5? X has not said. Customer acquisition and subscription revenue are plausible explanations, since the rate is one of the benefits of the paid plans, but we found no published account of how X funds it. A rate about 190 basis points above Treasury bills is a marketing choice X can revisit.

The tax mismatch: ordinary interest against a Section 1256 loss

X Money interest arrives on a 1099-INT. It is ordinary income, subject to state tax and, above $200,000 of income for single filers or $250,000 for joint filers, the 3.8% net investment income tax.⁸

The box’s financing cost is treated differently. SPX options are Section 1256 contracts: they are marked to market at year end, and gains and losses are treated as 60% long-term and 40% short-term regardless of how long you held them.⁹ The amount owed on a short box grows toward its fixed payoff as expiration approaches, and that growth is recognized as a capital loss. What that loss is worth depends on what Schedule D nets it against:

• Short-term gains. The whole loss offsets income taxed at ordinary rates. This is the only case where the deduction matches the tax on the interest.
• Long-term gains only, the usual situation for someone who rebalances a buy-and-hold portfolio. The 60% long-term piece offsets long-term gains directly, and after netting the 40% short-term piece does too. The whole loss saves the long-term rate.
• No other gains. Up to $3,000 of net capital loss a year offsets ordinary income, and the rest carries forward.¹⁰ That $3,000 also reduces net investment income for the 3.8% tax.¹¹
• Losses already carried forward. One more capital loss adds to the pile and saves nothing this year.

In symbols, with interest $I$, box cost $C$, a tax rate $t_I$ on the interest and a value $v$ per dollar of box loss:

The trade breaks even when $I / C = (1 - v)/(1 - t_I)$. When $v$ equals $t_I$, interest that matches the box cost is enough. When it is lower, the deposit needs a cushion: at the top bracket with long-term gains, $(1 - 0.238)/(1 - 0.408) = 1.29$, so the interest must be 29% larger than the box cost. Here is the one-year result on $100,000 at a 5% box rate and 6% held all year, federal tax only:

$100,000, 12 months, $6,000 of interest, $5,000 of box cost, before commissions and state tax. “Both, 60/40” assumes enough short- and long-term gains to absorb each piece of the loss.

For the top-bracket investor with long-term gains, the deposit has to pay 6.44% just to break even at a 5% box rate. With short-term gains to absorb the loss, break-even is the box rate itself. For someone already carrying losses forward it is 8.45%. The lower brackets do better because the gap between ordinary and long-term rates is narrower: 24% against 15% instead of 40.8% against 23.8%.

Two details soften the picture for some readers. A box that spans December 31 is marked to market, so part of the loss lands in each tax year, roughly in step with the interest. And individuals can elect to carry a net Section 1256 loss back three years, but only against Section 1256 gains in those years.¹² Someone who has never traded futures or index options has nothing to carry it back against.

State tax mostly adds to both sides. Most states tax capital gains as ordinary income, so a usable box loss offsets the state tax on the interest at the same rate. Some do not allow capital losses against other income at all; New Jersey is one.

Where a margin loan fits this trade better

The box’s usual selling point is a lower rate than broker margin. At Interactive Brokers, the gap was small on November 5, 2026: IBKR Pro charged 5.38% on the first $100,000, 4.88% from $100,000 to $1 million, and 4.63% above that.¹³ A one-year box at 5.05% saves about a third of a point on a $100,000 loan and costs more than margin on the next dollar.

For this particular trade, margin also gets better tax treatment if you itemize. Interest follows the use of the borrowed money, and money deposited in an account counts as an investment expenditure.¹⁴ The margin interest is therefore investment interest, deductible on Schedule A up to your net investment income, which includes the X Money interest.¹⁵ It also reduces net investment income for the 3.8% tax.¹¹ The deduction offsets the interest at ordinary rates, which is the match the box loss usually fails to make.

For a 37%-bracket household, the 2026 limit on itemized deductions trims the federal value of each deducted dollar from 37% to 35%.¹⁶ Even so, on $100,000 at 5.38% for a year, with 6% held all year, the top-bracket itemizer keeps about $259 with margin against a loss of $258 with the box when the box loss would offset long-term gains. Without itemizing, the margin interest deducts nothing and the same trade loses about $1,828, worse than the box.

Margin also behaves differently in two ways that matter here. Its rate floats with the Fed, so if the Fed cuts and X follows, both sides fall together. That is a partial hedge: a promotional cut that X makes on its own still hurts. And a margin loan has no maturity date, which matters a great deal given the withdrawal limits below. The trade-off is that a fixed box rate protects you if rates rise. With the Fed’s target at 3.75% to 4.00% after a September hike, and two members voting for another hike on October 28, that is not a remote case.¹⁷ At brokers whose standard margin rates run 10% or more, margin loses on cost, and the box is the only cheap financing on offer.

X can change the rate at any time

An arbitrage locks both legs. This trade locks only the borrowing leg. The box obligation is fixed for its whole term; the 6% can change the next morning. X has already changed the terms several times in a few months. TechCrunch reported 6% as a benefit of the Premium+ plan in July 2026¹⁸ and as a boosted rate for direct-deposit customers in September.¹⁹ The current rate table took effect October 12, interest for New York residents ended October 1, and the $150,000 cap starts December 1.

The exposure also runs in one direction. X has little reason to raise a promotional rate that already sits about 190 basis points above Treasury bills, and every reason to trim it if the cost outruns the marketing value. Holding a fixed liability against that rate is a bet that the promotion outlasts the box. On $100,000 at a 5% box rate:

• If 6% holds for three months and then drops to 4%, the year earns about $4,496 of interest and loses about $504 before tax. For the top-bracket investor with long-term gains, the loss after tax is about $1,148.
• Before tax, 6% has to last about half the year at a 5% box rate for a cut to 4% to leave the trade even. After tax, for that same top-bracket investor, even a full year at 6% falls short.
• Losing the direct-deposit qualification has the same effect. If the paycheck moves or a pay date slips outside a 34-day window, the rate falls to 4% unless you pay for a subscription. Premium lists at $30 a month.²⁰

Shorter boxes pair better with a rate that can change at any time. A box expiring in December 2026 cost 4.38% on November 2, which widens the spread and limits how long you are committed. The cost is a new trade at each roll, with commissions, bid/ask, and whatever rate the market offers that day.

Getting the cash back before the box settles

When a short box expires, your broker settles the fixed obligation in cash. If the cash is still at X, you need to move it back in time, and X’s account agreement lists these default limits:³

The agreement tells users to check the app for “limits specific to your use,” and lists no default limit on ACH transfers into the account, so your numbers may differ. At the defaults, $100,000 takes 14 months to withdraw, longer than a one-year box runs. Standard ACH transfers out are free and take one to three business days; instant transfers cost 1.75%, which on $100,000 is $1,750, more than the year’s spread before tax.⁷ Money that X has swept to partner banks “may take more than one (1) business day” to withdraw.³

If the cash cannot get out in time, the broker settles the box from whatever else is in the account: it sells securities, or the shortfall becomes a margin loan at the broker’s rate. Rolling into a new box before expiration avoids moving the cash mid-trade, but the final unwind still runs into the same limits.

Collateral and platform risk

The box’s payoff is fixed, but the account that carries it moves with the market. A short box is backed by the other securities in your brokerage account, and once its proceeds have left for X, a market drop can trigger a maintenance call on that collateral. FINRA’s required margin disclosure says the firm “can sell your securities or other assets without contacting you.”²¹ Cboe’s own explainer for advisors makes the same point about box financing.²² The box spread loans guide works through how far a portfolio can fall before a call. The danger here is the combination: the call arrives when markets are falling, and the cash that could meet it is at X, behind a monthly withdrawal limit.

The deposits sit at Cross River Bank, and X sweeps balances to partner banks through IntraFi for up to $10 million of FDIC coverage per ownership category. The agreement says there is no guarantee every dollar stays insured, and it says the records X Payments keeps “will be used to establish your eligibility for deposit insurance.”³ X Payments is not a bank, and the FDIC says its insurance “does not protect against the insolvency or bankruptcy of a nonbank company.”²³ When Synapse, a middleware company that kept ledgers for several fintech apps, filed for bankruptcy in April 2024, partner banks found a shortfall of $60 million to $90 million, and the CFPB says customers lost access to their funds for weeks or months.²⁴ Nothing suggests X has the same problems. Still, a frozen account is an inconvenience for a saver and can force a liquidation for someone with a box due.

Run your own numbers

The calculator runs the trade with either financing, your tax rates, and a rate cut if you want one. The bar chart shows how much the answer moves with what the box loss offsets.

When the trade can work

The trade makes money after tax when several conditions hold at once:

• The box loss offsets short-term gains, or you are in a bracket where the ordinary and long-term rates are close. A small position helps too: with no other gains, a loss under $3,000 offsets ordinary income in full.
• A paycheck already lands at X by direct deposit, so the 6% costs nothing extra.
• The balance stays at or under $150,000. Above it the extra dollars earn 4% against a 5% loan; $250,000 nets $500 before tax for the year, and $500,000 loses $2,000.
• You have checked your withdrawal limits in the app, or you have other cash to settle the box.
• The collateral could absorb a bear market without a call, and you could live with the trade if X cut the rate the week after you opened it.

Even then, the most a 1% spread can earn on $150,000 is $1,500 a year before tax. For a reader who already has cash, there is a simpler question: whether X Money beats Treasury bills or a money market fund on that cash after state tax. Our SGOV vs. T-bills and where to park cash guides cover that comparison without any borrowing.

How Summitward helps

If you do borrow against a portfolio, track the loan as a liability next to the cash set aside to repay it, so the same dollars are not counted as both an emergency fund and the box settlement.

Frequently asked questions

Does money transferred from a brokerage earn X Money’s 6%?

Yes, if the account qualifies. The 6% depends on $1,000 of qualifying deposits (payroll-style ACH or an X creator payout) in a trailing 34 days, or a Premium or higher subscription. Once the account qualifies, the whole balance earns 6%, up to $150,000 from December 1, 2026. Whether the brokerage transfer itself counts toward the $1,000 depends on how the sending firm codes it; X looks for the PPD code that payroll deposits carry.

Is the cost of a box spread loan tax deductible?

Not as interest. It is a Section 1256 capital loss, 60% long-term and 40% short-term. It offsets capital gains, then up to $3,000 of ordinary income a year, with the rest carried forward. Margin interest on money parked in an interest-bearing account is investment interest, which itemizers can deduct against investment income.

Is borrowing with a box to earn a higher deposit rate an arbitrage?

No. An arbitrage locks in both sides. The box locks the borrowing cost until expiration, but X can change the deposit rate at any time, and the tax treatment of the two sides differs.

Why not just buy Treasury bills?

For cash you already have, compare them directly. Treasury bill interest is exempt from state and local income tax and X Money interest is not, so the 6% shrinks more in a high-tax state. A 13-week bill yielded 4.10% on November 5, 2026.²⁵ Borrowing to buy bills makes no sense at these rates, since the box costs more than the bill pays.

Does FDIC insurance cover this trade?

It covers the deposits if a bank holding them fails, subject to the conditions for pass-through coverage. It does not cover a rate cut, a failure at X Payments itself, a delay in getting money out, or anything that happens to the brokerage account carrying the box.

What if the Fed raises rates?

A box locked at 5% would then look cheap against a margin loan, whose rate rises with the Fed. Whether it helps the trade depends on X: the standard 4% rate might rise with market rates, but nothing obliges X to raise the promotional 6%.

Key takeaways

• The pre-tax spread is real: 5.05% for a November 2027 box on November 2, 2026, against 6.00% APY at X Money for qualifying accounts. That is $1,000 on $100,000 for a year.
• For a top-bracket investor whose gains are long-term, that $1,000 becomes a loss of about $258 after federal tax, because the box loss saves 23.8% and the interest is taxed at 40.8%.
• What the box loss offsets decides the result. Short-term gains, a lower bracket, or a loss under $3,000 with no other gains can make it profitable after tax.
• For itemizers, an IBKR Pro margin loan costs about the same as the box, deducts against the interest at ordinary rates, floats with the Fed, and has no repayment date.
• X can change the 6% without notice, caps it at $150,000 from December 1, 2026, and by default limits withdrawals to $7,500 a month. Check your in-app limits before trading against a fixed settlement date.

Related guides

• Box spread loans covers the mechanics, rate conventions, collateral math and the full tax treatment of borrowing with SPX boxes.
• 0% APR arbitrage runs the same kind of borrow-and-deposit trade with a credit card promotion.
• BOXX ETF explained is the lending side of the box market.
• Borrow or sell for the down payment compares box loans, margin and selling for a short, dated cash need.
• SGOV vs. T-bills compares two state-tax-exempt places to hold cash you already have.

Sources and method

1. Boxtrades, SPX Box Spread Yield Curve, last updated November 2, 2026, 1:02 PM. Volume-weighted mean implied rates by expiration, before brokerage and exchange fees: Dec 18, 2026 4.38%; Feb 19, 2027 4.68%; May 21, 2027 4.83%; Nov 19, 2027 5.05% (nine trades). L-ETF’s compilation of the same data showed 5.04% for November 2027. Boxtrades, L-ETF
2. X Money, Interest FAQ, rate table effective October 12, 2026. 4.00% APY standard; 6.00% for Premium, Super and Ultra subscribers, legacy Premium+ subscribers, or with $1,000 of qualifying deposits (ACH SEC code PPD, or an X creator payout) in a trailing 34 days; 6% on the first $150,000 from December 1, 2026. X Money
3. Cross River Bank, X Money Stored Value Account Agreement, read November 5, 2026. Section 6 transfer limits; Appendix 3 (interest may change or be discontinued); Appendix 4 (IntraFi sweep, coverage not guaranteed, withdrawals from network banks may take more than one business day, X Payments records used for insurance eligibility). X Money
4. U.S. Department of the Treasury, Daily Treasury Par Yield Curve Rates, November 2, 2026: 1-month 4.05%, 3-month 4.21%, 6-month 4.25%, 1-year 4.38%. Treasury
5. Jules van Binsbergen, William Diamond and Peter Van Tassel, Options for Calculating Risk-Free Rates, Liberty Street Economics, Federal Reserve Bank of New York, October 2, 2023. See also van Binsbergen, Diamond and Grotteria, Risk-Free Interest Rates, Journal of Financial Economics 143(1), 2022, 1–29. New York Fed, RePEc
6. Julian Kozlowski and Nicholas Sullivan, Are U.S. Treasuries Still “Convenient”?, On the Economy, Federal Reserve Bank of St. Louis, October 14, 2025. Data through August 29, 2025; the annual averages include negative values in 2023 and 2024. St. Louis Fed
7. X Money, FAQ, read November 5, 2026. Balance cap example, New York interest ending October 1, 2026, ACH and instant transfer fees, daily compounding and monthly crediting, 1099-INT. X Money
8. Internal Revenue Service, Net Investment Income Tax. IRS
9. Internal Revenue Service, Publication 550, Investment Income and Expenses, Section 1256 contracts marked to market; and Form 6781. IRS, Form 6781
10. 26 U.S.C. §1211(b) and §1212(b), $3,000 limit on net capital losses against ordinary income, and carryforward. Cornell LII
11. Treas. Reg. §1.1411-4, paragraph (d), Example 1 (the $3,000 allowed under §1211(b) reduces net investment income), and paragraph (f)(3)(i) (investment interest allowed under §163(d) is a properly allocable deduction). Cornell LII
12. 26 U.S.C. §1212(c), election by individuals to carry a net Section 1256 loss back three years against net Section 1256 gains. Cornell LII
13. Interactive Brokers, Margin Rates, read November 5, 2026. IBKR Pro USD: benchmark 3.88% plus 1.5% to $100,000 (5.38%), 1% to $1 million (4.88%), 0.75% to $50 million (4.63%). Interactive Brokers
14. Treas. Reg. §1.163-8T(c)(4)(i), debt proceeds deposited in an account are treated as an investment expenditure, and amounts held in the account as property held for investment. Cornell LII
15. 26 U.S.C. §163(d), investment interest limited to net investment income; qualified dividends and net capital gain count only by election under §163(d)(4)(B). Reported on Form 4952. Cornell LII
16. 26 U.S.C. §68, as amended by Public Law 119-21 (2025): for taxpayers in the 37% bracket, itemized deductions are reduced by 2/37 of the lesser of the deductions or taxable income above the 37% threshold, starting in 2026. Cornell LII
17. Federal Reserve, FOMC statement, October 28, 2026: target range held at 3.75% to 4.00%, with two members preferring an increase. Federal Reserve
18. Amanda Silberling, Elon Musk’s X Money app is rolling out in the U.S., TechCrunch, July 28, 2026. TechCrunch
19. Sarah Perez, X shifts US creator payouts from Stripe to X Money, TechCrunch, September 2, 2026. TechCrunch
20. xAI, X Subscription pricing, read November 5, 2026: Plus $8, Premium $30, Super $100 and Ultra $200 a month, before tax. xAI
21. FINRA Rule 2264, Margin Disclosure Statement. FINRA
22. Rick Rosenthal, SPX Box Spreads: What Every Advisor Should Know, Cboe, March 12, 2026. Cboe
23. FDIC, Banking With Third-Party Apps, updated May 31, 2024. FDIC
24. Consumer Financial Protection Bureau, Synapse Financial Technologies, Inc., enforcement action. Chapter 11 filing April 22, 2024; shortfall of $60 million to $90 million. CFPB
25. U.S. Department of the Treasury, Daily Treasury Bill Rates, coupon-equivalent, November 5, 2026: 4-week 3.96%, 13-week 4.10%, 26-week 4.22%, 52-week 4.28%. Treasury
26. Method. Every dollar figure above comes from web/src/lib/box-carry-math.ts, which is unit tested against the tables above. Interest compounds at the quoted APY on the starting balance; the box cost compounds at the quoted annual rate; margin interest accrues simply. Federal rates are the marginal rates shown, with the 3.8% net investment income tax where noted, and no state tax unless stated. A box loss offsetting long-term gains is valued at the long-term rate, against short-term gains at the ordinary rate, against both at the 60/40 blend, and with no other gains at the ordinary rate on the first $3,000. Carryforwards are valued at zero in the year. Margin interest is valued at 35% plus 3.8% for a 37%-bracket itemizer and capped at the deposit interest. Commissions, bid/ask on the box and margin calls are not modeled. Nothing here is tax, legal or investment advice.