SoftBank Shares Tumble as $64.6B OpenAI Stake Raises Leverage Concerns

SoftBank Group Corp. shares tumbled after the company finalized a multi-billion dollar investment program in OpenAI, with investor focus shifting to the significant leverage and concentration risk associated with its now $64.6 billion stake in the artificial intelligence leader.

Investor Scrutiny Follows Deal Completion

Shares of SoftBank (TSE: 9984) fell 6.0% to ¥6,296 in Tokyo trading on October 2, reversing gains seen just days earlier. The drop came after the firm completed a final $10 billion payment to OpenAI on October 1, concluding a $30 billion program and bringing its total investment to $64.6 billion for an approximate 13% stake.

Market sentiment has turned cautious, viewing the massive position as a significant concentration risk. SoftBank has effectively become a leveraged proxy for the performance of a single, privately held AI company.

The High Cost of Financing

The final investment tranche was financed through an $11.1 billion sale of high-yield bonds. According to a September 23 filing cited by the source, these junk-rated notes carry steep interest rates of 8.625% to 9.75%. The source states this debt has caused SoftBank's finance costs to roughly double in its first fiscal quarter.

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Adding to the burden, OpenAI does not pay a dividend, meaning there is no investment income to offset the hundreds of millions in annual interest costs. Reflecting bond market anxiety, the price of SoftBank's credit default swaps—a form of insurance against default—recently hit its highest level since 2023.

Valuation Risks and Loan Covenants

A critical risk stems from a $10 billion loan backed by SoftBank's OpenAI shares. An analysis dated September 14 indicated that if the value of those shares were to "decline substantially," SoftBank could be forced to post more cash or repay the loan prematurely.

This structure creates a potential negative feedback loop where a downturn in AI sentiment could depress OpenAI's private valuation, triggering a margin call that forces SoftBank to sell assets at an inopportune time. The valuation itself is a model-based estimate, not a liquid market price. As of June 30, SoftBank recorded a paper gain, valuing its stake at $89.6 billion against a cost of $44.6 billion.

Despite these concerns, the potential for a significant upside remains a powerful draw. Reports suggest OpenAI may be raising new capital at a valuation of around $1.4 trillion, a substantial step up from the $852 billion of its last round. However, for investors, the immediate focus is on the financial risks created by the highly leveraged financing of this transformative bet.