Microsoft's financial dependency on OpenAI is far greater than previously known to the public.

According to documents filed by Microsoft last week, the company generated $24.1 billion in revenue from OpenAI in the fiscal year ending June 2025. This figure indicates that OpenAI contributed more than half, and potentially up to 70%, of Microsoft's total AI business revenue.

This disclosure has drawn significant attention from investors. The market has long questioned the true composition of Microsoft's AI revenue, and this data shows that even as Microsoft repeatedly emphasizes the continuous expansion of its AI landscape, its core growth driver remains heavily concentrated on a single source.

KeyBanc analyst Jackson Ader stated that whether OpenAI's contribution comes from cloud computing services or revenue-sharing agreements remains a key unanswered question.

As of press time, Microsoft's stock was down 0.5% in midday trading on Wednesday.

$24.1 Billion: OpenAI's Contribution to Microsoft

In regulatory filings submitted last week, Microsoft disclosed that it recorded $24.1 billion in sales from OpenAI for the fiscal year ending June 2025.

Microsoft CEO Satya Nadella previously stated that the company's AI business had an annualized revenue run rate of approximately $37 billion as of the end of the March quarter. However, Microsoft did not update this aggregate figure when reporting its fourth-quarter results last week.

According to Bloomberg calculations, based on Microsoft's 123% year-over-year growth rate disclosed in the March quarter, the company's AI business revenue for the fiscal year ending June 2025 would be approximately $34 billion. On this basis, the $24.1 billion provided by OpenAI accounts for about 70% of that total.

Microsoft has only publicly disclosed the overall scale of its AI business twice: once in the December 2024 quarter, with an annualized run rate exceeding $13 billion, and again in the March 2025 quarter, with an annualized run rate surpassing $37 billion.

The rapid growth between these two disclosures impressed the market, but the specific weight of OpenAI within this growth was only revealed in the latest filing.

Partnership Structure: How OpenAI Pays Microsoft

Under the agreement between the two companies, OpenAI pays Microsoft for computing power, costs related to AI model development, and a certain percentage of revenue sharing.

A Microsoft spokesperson confirmed that the $24.1 billion figure includes all sales and revenue sharing from OpenAI.

Jackson Ader noted that this composition is critical: "The more OpenAI's contributed revenue comes from providing services to it, as opposed to investment returns, the more positively I view this business."

His logic is that service revenue reflects genuine commercial delivery capabilities, rather than paper contributions from financial arrangements.

Microsoft Seeks to Diversify, Limited Success

Facing market concerns about concentration on a single source, Microsoft has been attempting to reduce its reliance on OpenAI in recent years. The company has provided support to rival Anthropic PBC and accelerated the development of its own AI models.

However, based on the disclosed data, these efforts have not yet achieved sufficient diversification at the revenue level.

Measured against total revenue, OpenAI's share is less than 10%—Microsoft added approximately $51 billion in commercial bookings in the last quarter, primarily driven by customers outside the AI startup sector.

But in terms of incremental annual bookings, OpenAI remains the largest contributor.

Disclosure Timing: Potentially Linked to OpenAI's IPO Plans

It is worth noting that the timing of this detailed disclosure is quite subtle.

Olga Usvyatsky, an accounting researcher and founder of data analytics firm Nonlinear Analytics, stated in a research report that the release of this information may be related to OpenAI's preparations for an initial public offering (IPO).

Prior to this disclosure, Microsoft had never explicitly released its full revenue data from OpenAI.

As OpenAI moves toward the public market, the financial relationship between the two companies will face stricter scrutiny, and investors will demand greater transparency regarding the structure of their partnership.