OpenAI may be burning far more capital serving its GPT-family of models than previously thought. Leaked documents show the company paying more than $12 billion to Microsoft for compute power since 2024 and suggest much weaker revenue than it needs to pay for all those expenses.

According to internal Microsoft financial documents [1]obtained by AI skeptic and tech blogger Ed Zitron, OpenAI blew $8.7 billion serving its models, a process called inference, on Azure alone in the first three quarters of 2025. That's more than double the $3.7 billion the AI flag bearer reportedly spent in 2024.

If the info in these leaks are correct, OpenAI's expense line is even worse than it looks at first blush. The report, we'll note, didn't include details on any training-specific spend at the cloud provider. It also does not mention CoreWeave and Google, which OpenAI also pays for compute capacity.

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Using these numbers, OpenAI would be on a trajectory to far exceed the $9 billion in cash burn previously [3]reported by the Wall Street Journal earlier this week.

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However, there's reason to believe these documents may not provide a full picture as to OpenAI's financial relationship with its long-time compute partner, Microsoft.

According to the [6]Financial Times , which also got a look at the documents, a Microsoft spokesperson said "the numbers aren't quite right," but declined to comment further. Another source familiar with OpenAI suggested to the FT that the figures offered an incomplete accounting of the two company's dealings.

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One possibility is that these documents may not account for the possibility of cloud credits Microsoft granted to OpenAI. Those credits would likely end up lumped with other customers and show up under cost of sales in Microsoft's accounting. In that case, depending on how Microsoft has chosen to engineer its books, the figures in the report may inflate the amount of cash OpenAI is actually spending on inference with Azure each quarter.

Then there's the revenue side of the picture. Zitron's report also suggests that OpenAI's sales may be significantly smaller than its previous reports about annual recurring revenues (ARRs) imply.

Also on Wednesday, OpenAI rival Anthropic [8]announced a $50 billion investment in US datacenter infrastructure in collaboration with Fluidstack.

The collaboration will see the construction of several large datacenters in Texas and New York. The announcement didn't address how the AI startup would pay for said datacenters, what silicon would power them, or the timeline over which they'd be built. The AI startup did suggest that, when complete, the project would create around 800 permanent jobs, each paying on average $144,000. ®

These details are based on a 20 percent revenue share that OpenAI pays Microsoft under the company's initial $1 billion tie-up in 2019. Under that deal, Microsoft also pays OpenAI a 20 percent slice of revenue from the resale of OpenAI models and services under its brand.

The documents show Microsoft received $454.7 million from OpenAI during the first half of calendar year 2025. Taking into account the 20 percent revenue share, this suggests that OpenAI's sales during the period were approximately $2.27 billion.

As Zitron notes, that's approximately $2 billion short of the $4.3 billion in revenues The Information [9]reported in early October.

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The documents indicate that OpenAI's revenues surged in the quarter ended Sept. 30, with Microsoft's share of sales reaching $865.9 million through that quarter, putting OpenAI's calculated revenues at $4.33 billion.

In spite of the jump, these figures are still in conflict with statements OpenAI CEO Sam Altman [11]made earlier this month that the company's annual revenues would exceed $13 billion.

However, just like OpenAI's inference spend, it's possible that the figures contained within the report are incomplete. As mentioned earlier, Microsoft also pays OpenAI a 20 percent share of revenues from reselling the AI dev's models.

[12]Superintelligence probably not happening, but AI will still reshape society, expert panel says

[13]Altman sticks a different hand out, wants tax credits instead of gov loans

[14]Meta can't afford its $600B love letter to Trump

[15]OpenAI's Altman and Friar walk back remarks about federal loan guarantees

The documents appear to apply only to Azure. But Microsoft may be paying OpenAI separately out of other segments within its software business. Microsoft integrates OpenAI products into several products including its Bing search engine, Office 365 productivity Suite, GitHub copilot code assistant. Unfortunately, Microsoft has yet to break out AI-related revenues in the associated fields.

However, Redmond's own financial reporting did [16]indicate that OpenAI had a net loss in the neighborhood of $12 billion during the quarter ended Sept. 30.

If nothing else, Wednesday's reports underscore the need for greater financial transparency from OpenAI and its partners. Customers planning for the AI revolution need to understand if the finances don't work, as that would imply either a slower buildout or higher prices than expected.

El Reg reached out to Microsoft and OpenAI for their comment. Microsoft declined, and OpenAI did not respond by press time. ®

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[1] https://www.wheresyoured.at/oai_docs/?ref=ed-zitrons-wheres-your-ed-at-newsletter

[2] https://pubads.g.doubleclick.net/gampad/jump?co=1&iu=/6978/reg_software/aiml&sz=300x50%7C300x100%7C300x250%7C300x251%7C300x252%7C300x600%7C300x601&tile=2&c=2aRURh1Paq_zTlTfekcwzQwAAAAo&t=ct%3Dns%26unitnum%3D2%26raptor%3Dcondor%26pos%3Dtop%26test%3D0

[3] https://www.wsj.com/tech/ai/openai-anthropic-profitability-e9f5bcd6?mod=tech_lead_story&ref=wheresyoured.at

[4] https://pubads.g.doubleclick.net/gampad/jump?co=1&iu=/6978/reg_software/aiml&sz=300x50%7C300x100%7C300x250%7C300x251%7C300x252%7C300x600%7C300x601&tile=4&c=44aRURh1Paq_zTlTfekcwzQwAAAAo&t=ct%3Dns%26unitnum%3D4%26raptor%3Dfalcon%26pos%3Dmid%26test%3D0

[5] https://pubads.g.doubleclick.net/gampad/jump?co=1&iu=/6978/reg_software/aiml&sz=300x50%7C300x100%7C300x250%7C300x251%7C300x252%7C300x600%7C300x601&tile=3&c=33aRURh1Paq_zTlTfekcwzQwAAAAo&t=ct%3Dns%26unitnum%3D3%26raptor%3Deagle%26pos%3Dmid%26test%3D0

[6] https://www.ft.com/content/fce77ba4-6231-4920-9e99-693a6c38e7d5

[7] https://pubads.g.doubleclick.net/gampad/jump?co=1&iu=/6978/reg_software/aiml&sz=300x50%7C300x100%7C300x250%7C300x251%7C300x252%7C300x600%7C300x601&tile=4&c=44aRURh1Paq_zTlTfekcwzQwAAAAo&t=ct%3Dns%26unitnum%3D4%26raptor%3Dfalcon%26pos%3Dmid%26test%3D0

[8] https://www.anthropic.com/news/anthropic-invests-50-billion-in-american-ai-infrastructure

[9] https://www.theinformation.com/articles/openais-first-half-results-4-3-billion-sales-2-5-billion-cash-burn

[10] https://pubads.g.doubleclick.net/gampad/jump?co=1&iu=/6978/reg_software/aiml&sz=300x50%7C300x100%7C300x250%7C300x251%7C300x252%7C300x600%7C300x601&tile=3&c=33aRURh1Paq_zTlTfekcwzQwAAAAo&t=ct%3Dns%26unitnum%3D3%26raptor%3Deagle%26pos%3Dmid%26test%3D0

[11] https://fortune.com/2025/11/01/sam-altman-openai-annual-revenue-13-billion-forecast-100-billion-2027/?ref=wheresyoured.at

[12] https://www.theregister.com/2025/11/11/ai_experts_forecast/

[13] https://www.theregister.com/2025/11/10/altman_ai_tax_credit/

[14] https://www.theregister.com/2025/11/08/meta_cant_afford_its_600b/

[15] https://www.theregister.com/2025/11/06/openai_cfo_walks_back_remarks/

[16] https://www.theregister.com/2025/10/29/microsoft_earnings_q1_26_openai_loss/

[17] https://whitepapers.theregister.com/