CFO Christopher Eperjesy's Equity Transactions at Custom Truck One Source

This Form 4 filing reports equity transactions by Christopher J. Eperjesy, Chief Financial Officer of Custom Truck One Source, Inc. (CTOS), on April 1, 2026. The filing includes multiple restricted stock unit transactions: 22,500 RSUs vested and settled (leaving 0 remaining), 45,000 RSUs partially vested (leaving 45,000 remaining), 22,500 RSUs partially vested (leaving 67,500 remaining), and a new grant of 95,000 RSUs that vest in four annual installments beginning April 1, 2027. Additionally, 90,000 shares of common stock were acquired through RSU settlement, while 40,547 shares were disposed of at $6.62 per share to cover tax obligations. Following these transactions, Eperjesy holds 283,926 shares of common stock directly and maintains various RSU positions. The filing was signed by attorney-in-fact Paul M. Jolas on April 3, 2026.