Bill Ackman Moves into Microsoft; Size Disclosed Today
May 15, 2026 – 9:30 am
Image by: Harvard Law School
Pershing Square has taken a new position in Microsoft, with the size to be disclosed later today in a 13F filing. The stock is down approximately 16% year-to-date.
Bill Ackman has bought Microsoft. Pershing Square’s CEO stated on X this morning that the fund had acquired a new stake in the software company following its recent share price decline, with details to be revealed in a regulatory filing later today.
Ackman’s rationale: The market is undervaluing Microsoft’s enterprise franchise rather than its AI capabilities. Investors have underestimated Microsoft’s software given its "deeply embedded role across enterprises and highly attractive price-value proposition," he wrote, positioning the investment as a quality-compounder play on the established base rather than a bet on Azure capex.
The timing of the trade is significant. Microsoft shares have dropped roughly 16% year-to-date, trading near $413 since late April when CFO Amy Hood raised full-year capital expenditure guidance to approximately $190 billion—substantially exceeding analysts’ expectations of around $155 billion.
Ackman has executed a similar strategy this year. In February, Pershing Square disclosed a new stake in Meta, three weeks after the social media giant’s own capex-driven sell-off, with Ackman describing the investment as a "deeply discounted valuation" at the time.
The Microsoft entry follows a similar pattern: a megacap stock depressed by AI spending guidance, framed by Ackman as an opportunity to acquire a high-quality franchise at a temporarily reduced multiple.
Friday is expected to be a busy day for hedge fund disclosures as funds with over $100 million in assets under management are required to file Form 13F within 45 days of the quarter end. Pershing Square’s last 13F, covering December, revealed eleven positions and approximately $16 billion in disclosed US holdings concentrated in Brookfield, Uber, Amazon, Alphabet, and Meta; Microsoft was not included. Today’s filing will reveal whether the firm has reduced existing positions to fund this new one or sized it from cash.
The investment also fits into a wider debate about AI infrastructure. Hyperscalers have committed over $650 billion to AI capex across 2026, based on Q1 numbers from Microsoft, Alphabet, Amazon, Meta, and Apple. The market is now questioning whether this spend will translate into operating earnings.
Ackman argues that Microsoft’s existing Office, Windows, and Azure business is enough to meet expectations, independent of its AI optionality.