SoftBank Is Raising $11 Billion in Debt to Keep Feeding OpenAI: Inside the Bond Sale Funding the AI Arms Race

Masayoshi Son is going back to the bond market — and the reason is a single company. On Monday, September 21, SoftBank Group launched $10 billion and €1 billion in senior unsecured notes, according to a term sheet seen by Reuters, with the proceeds earmarked to fund its $10 billion payment for the third tranche of a follow-on investment in OpenAI, expected to close on October 1. The bonds will also cancel out a $10 billion bridge loan facility SoftBank had secured to fund the OpenAI investment.

Read that again slowly. One of the largest corporate bond sales of the year exists for one purpose: to keep the money flowing into a single AI lab. The AI arms race is no longer funded out of cash flow or venture rounds. It is now funded the way governments fund wars — with sovereign-scale debt.

SoftBank Group CEO Masayoshi Son (second from left) and OpenAI CEO Sam Altman (left) with Japanese Prime Minister Shigeru Ishiba in Tokyo, February 3, 2025. (Photo: Office of the Prime Minister of Japan, CC BY 4.0, via Wikimedia Commons)

The terms of the sale

The details, per the Reuters reporting on the term sheet, are precise. The dollar-denominated notes are split across three tenors — 3½-year, 5½-year, and 7½-year — while the euro-denominated bonds are split into 4-year and 6-year tranches. The issuances are expected to price on September 24 and settle on September 29. Citigroup and JPMorgan are the lead bookrunners. SoftBank could not be immediately reached for comment; Monday was a holiday in Japan.

The structure tells its own story. A bridge loan is, by definition, temporary — expensive, short-dated money meant to hold a position until permanent financing arrives. Replacing it with multi-year bonds across two currencies is what a borrower does when the spending is not a one-time event but a program. SoftBank is not bridging to a finish line. It is building a permanent funding pipeline into OpenAI.

The $40 billion foundation — and what comes after it

To understand the scale of what SoftBank is doing, rewind to late 2025. That December, SoftBank completed its landmark $40 billion investment in OpenAI — one of the largest private technology investments in history. The commitment was deployed in stages: roughly $10 billion syndicated to co-investors, $8 billion invested directly, and a final tranche of $22 to $22.5 billion that closed the round, according to CNBC's reporting at the time.

The $40 billion was never just a check. It was a strategic repositioning. To fund it, SoftBank sold its entire $5.8 billion stake in Nvidia — the single greatest beneficiary of the AI boom — and trimmed about $4.8 billion from its T-Mobile holding. It cut staffing at its Vision Fund. The message was unmistakable: the diversified venture era was over; the concentrated AI-infrastructure era had begun. A portion of the capital was earmarked for Stargate, the AI infrastructure joint venture with Oracle building a U.S.-wide network of AI data centers, and Nikkei Asia reported the investment left SoftBank holding roughly 11% of OpenAI — its largest shareholder after Microsoft.

Today's bond sale funds the next layer: a follow-on investment whose third tranche alone is $10 billion, closing October 1. SoftBank is not done. It is doubling down — with borrowed money.

Why debt, and why now

There is a reason the world's most aggressive technology investor is borrowing rather than selling. SoftBank has spent the last year liquidating the assets it was willing to part with — the Nvidia stake is gone, the T-Mobile trim is done. What remains is a portfolio increasingly concentrated in two things: Arm, and AI. Selling more of either would mean diluting the very positions the entire strategy depends on. Debt, at investment-grade terms, lets Son keep his equity exposure while adding leverage to the bet.

The timing matters too. OpenAI is reportedly in early-stage, investor-initiated talks for a pre-IPO round at a valuation above $1.2 trillion, with an IPO expected in 2027 — a story this publication covered earlier this month. Anthropic is targeting a November IPO. Every funding event reprices the sector upward, and every repricing makes the next tranche more expensive to miss. For SoftBank, the $10 billion October payment is not optional spending. It is the price of keeping its seat at the table it built.

The industry this debt is building

Step back, and the SoftBank bond sale is a window into how the AI economy now works. The Financial Times reported on September 20 that Big Tech companies hold roughly $300 billion of AI infrastructure exposure off their balance sheets through guarantees and special-purpose vehicles. U.S. spending on data centers and information-processing hardware has now surpassed housing investment. Hyperscalers are expected to be investing at a pace approaching $1 trillion a year.

In that world, SoftBank's $11 billion bond sale is not an outlier — it is the template. The AI buildout has outgrown the balance sheets of even the richest companies, so the industry is doing what industries always do at this stage of a boom: it is financializing. Bridge loans become bonds. Bonds become securitizations. Off-balance-sheet vehicles absorb the rest. The question is not whether the money is real — it is. The question is what happens to the edifice if the returns arrive slower than the interest payments.

What to watch: pricing day and October 1

Two dates will tell the rest of this story. The first is September 24, when the bonds price. The coupon SoftBank has to offer — the interest rate investors demand for lending $11 billion against an AI bet — will be the market's unspun verdict on how risky this trade looks from the outside. A tight spread means the bond market believes the AI buildout is a near-certainty; a wide one means even the optimists want to be paid for the doubt.

The second is October 1, when the third tranche is expected to close. Watch for what OpenAI says — or doesn't — about the follow-on round's total size and terms. Each tranche that closes without a public valuation event keeps the market guessing about what SoftBank is actually paying per share of the world's most valuable private company. And watch who else starts borrowing: if the debt-funded AI investment becomes a pattern rather than a Son idiosyncrasy, the industry's capital structure will have changed in a way that outlasts any single funding round.

The Son doctrine

None of this is out of character. Masayoshi Son has spent three decades making the same bet at increasing scale: that the future arrives faster than the skeptics think, and that the way to win it is to deploy overwhelming capital before the consensus forms. He did it with broadband, with Alibaba, with the Vision Fund's $100 billion blitz. The misses — WeWork most famously — were spectacular, but the doctrine never changed.

The OpenAI bet is the doctrine's final form. Son sold Nvidia, the picks-and-shovels winner of the AI boom, to buy more of the company digging the mine. He is now borrowing $11 billion to buy more still. If OpenAI's trajectory justifies a trillion-dollar valuation, the leverage will look like genius. If the AI investment cycle turns — if enterprise returns disappoint, if a competitor breaks the scaling paradigm, if regulation bites — the debt will still be there, in dollars and euros, priced September 24 and settling September 29, long after the narratives move on.

For now, the bond market is voting with its wallet. The pricing on Thursday will tell us exactly how much it believes.

Sources: Reuters (Sept. 21, 2026, reporting by Kane Wu); CNBC (Dec. 2025); Nikkei Asia; Financial Times (Sept. 20, 2026, via FourWeekMBA). Related TechPulse USA coverage: OpenAI eyes a $1.2 trillion pre-IPO round; Factory AI triples to a $5 billion valuation.