William Von Mueffling's Cantillon Capital Management significantly reduced its position in Interactive Brokers (IBKR) by 95.40% during the second quarter of 2026. According to a quarterly 13F filing, which discloses positions held as of June 30, 2026, the firm sold over 10.7 million shares, reducing its holding to just 517,833 shares from a previous 11.25 million. This massive sell-off had an estimated trade value of $933.77 million.
Despite this substantial reduction, the remaining Interactive Brokers stake now represents a larger portion of Cantillon's reported portfolio, increasing from 5.01% to 6.78%. Investors are reminded that 13F filings are delayed disclosures and reflect portfolio changes from the previous quarter, not necessarily the firm's current holdings or a single day's trading activity.