Sam Altman’s OpenAI Confidentially Files for IPO, Eyes $850+ Billion Valuation

OpenAI just took its most concrete step yet toward Wall Street, while going out of its way to say it has not actually decided to go public. The company confidentially filed S-1 IPO paperwork with the SEC and disclosed the move in a blog post. OpenAI was valued at roughly $850 billion after its $122 billion financing round in March. According to CNBC’s Kate Rooney, “OpenAI did take a major step towards a public market debut with this confidential filing that it put into the SEC. The company acknowledged that, saying, ‘We expect it to leak. So we’re just announcing it.'”

The Filing and What It Means

A confidential SEC filing is a preparatory step. It lets a company assemble an S-1 with the regulator behind closed doors, preserving optionality on timing without forcing public disclosure of financials. OpenAI explicitly framed the move as preserving choice, calling going public “a complicated set of trade-offs” and saying the filing simply gives the company the option to move quickly if it chooses.

On timing, Rooney reported: “I am also told by a source at OpenAI, it could go as soon as September, although market conditions will be a big factor.” That is a conditional possibility dependent on market conditions.

An Unprecedented IPO Wave

The filing lands in the middle of what is shaping up to be a historic year for mega-cap debuts. Anthropic, valued at around $965 billion, confidentially filed its own IPO paperwork a week earlier, and SpaceX is set to begin trading within days. Polymarket traders currently assign a 68.5% probability to an OpenAI IPO by December 31, 2026, but only a 31% probability for a September listing, and a 24.5% probability that no IPO occurs by year-end at all. Traders pricing the closing market cap on day one assign a 45.9% probability to a debut north of $1.5 trillion.

Why Staying Private Still Makes Sense

Per Pitchbook, OpenAI is spending $2.20 for every $1 earned, a burn rate driven by what Rooney described as “hundreds of billions of dollars” in data-center spending. A public listing subjects that figure to quarterly scrutiny. Whether OpenAI has a credible path to profitability that justifies an $850 billion valuation is the question every prospective IPO buyer must answer.

OpenAI itself flagged the case for not listing. As Kate Rooney noted, “Being a private company allows them to move a lot faster. You don’t need quarterly earnings. You don’t need all of the shareholder approval. That obviously comes with being a public company.” The company also plans to let employees sell shares via a tender offer at the current valuation, which relieves the internal liquidity pressure that often forces a company to go public. A business burning $2.20 per $1 of revenue may simply prefer to scale without the quarterly leash.

The Microsoft Angle

Until OpenAI actually lists, Microsoft (NASDAQ:MSFT | MSFT Price Prediction) remains the most direct public proxy. Following the partnership restructuring disclosed in Microsoft’s Q1 FY26 earnings, Microsoft holds an approximately 27% stake in OpenAI valued at around $135 billion, and OpenAI contracted to purchase an incremental $250 billion of Azure services (see the SEC filing). An IPO at the implied $850 billion level would mark-to-market that stake at a level well above its current carrying value.

Microsoft’s own AI business is already strong. In Q3 FY26 (reported April 29, 2026), revenue rose 18.3% year over year to $82.89 billion, EPS came in at $4.27, and CEO Satya Nadella said: “Our AI business surpassed an annual revenue run rate of $37 billion, up 123% year-over-year.” Shares trade at $411.74, down 14.48% year to date, even as analysts carry a consensus price target of $560.95.

The Takeaway

OpenAI’s confidential filing is an important milestone for the AI sector and the broader IPO wave. The filing gives the company additional optionality, but its reported $2.20 of spending for every $1 of revenue keeps the path to profitability front and center for investors. Whether a September debut remains on the table will largely depend on market conditions. For now, OpenAI remains private, leaving Microsoft as the closest public-market proxy for investors seeking exposure.

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