Executive Summary:Microsoft disclosures and Bloomberg analyses show that OpenAI's compute spend and revenue share accounted for 70% or more of Microsoft's FY26 AI revenues, and more than 7% of Microsoft's overall FY2026 revenues. OpenAI accounted for $24.1 billion of Microsoft's FY2026 revenues. As I discussed in yesterday's free newsletter, analyst estimates have OpenAI and Anthropic making up over 70% of all AI revenues across Microsoft, Google and Amazon. While some might have disagreed, Bloomberg is now reporting that OpenAI "accounted for more than half, and likely about 70%, of Microsoft's actual AI sales during its most recent fiscal year." The other incredible fact from these disclosures is that OpenAI's spend and revenue share accounted for 7% of Microsoft's $331.8 billion in FY26 revenue - or around 7.26% to be specific.