The "Taxpayer-Funded Union Time Transparency Act" requires federal agencies to submit comprehensive annual reports to Congress and publicly post them on their websites. These reports must detail the use and cost of official time , which is time federal employees spend on union activities while still being paid by the government, as authorized under section 7131 of title 5, United States Code. Each report must include the total cost of official time, a detailed explanation for its authorization, and specific data for employees utilizing it, such as their position, pay, benefits, and the exact percentage of their work hours spent on official time. Agencies must also disclose total compensation paid for negotiating collective bargaining agreements, processing grievances, and engaging in dispute resolution processes, along with fees paid to arbitrators and travel expenses. The bill further mandates reporting on the value of agency property and real estate made available to labor organizations at no cost or a discounted rate, including related administrative support costs. It also requires an explanation for any year-over-year increase in authorized official time and the total amount of penalties levied against the agency related to collective bargaining. The Comptroller General is tasked with auditing agency accounting practices for these reports at least every four years, briefing Congress if agencies fail to use generally accepted accounting principles.