This bill, known as the Fiscal Sponsorship Transparency Act of 2026, aims to increase transparency and prevent abuse within fiscal sponsorship arrangements by amending the Internal Revenue Code. It requires certain charitable organizations to report detailed information about each fiscal sponsorship arrangement in effect during the taxable year. This includes the names of parties involved, aggregate amounts made available or transferred, a description of related activities, the principal officer managing the arrangement, and its start and end dates. The legislation defines a "fiscal sponsorship arrangement" as one where an exempt organization receives and administers funds for a non-exempt person or publicly solicits for a specific project, crucially requiring the organization to retain discretion and control over the funds. Furthermore, the bill disallows charitable contribution deductions for gifts made under an "improper conduit arrangement," which is defined as soliciting or receiving contributions for a non-exempt person without the organization exercising discretion and control. New excise taxes are imposed on organizations and their managers for knowingly participating in such improper arrangements, with initial taxes of 20% on the organization and 5% on managers, and additional taxes of 100% and 50% respectively if not corrected. These amendments will apply to taxable years beginning after December 31, 2027.