This bill, titled the Taxpayer-Funded Union Time Transparency Act, aims to enhance transparency regarding federal employees' use of official time for union activities and other labor-related expenditures within federal agencies. It mandates that the head of each agency submit an annual report to Congress and publicly post it online, detailing various costs and resources associated with labor matters. This report must cover the total cost of official time authorized under Section 7131 of Title 5, United States Code, along with a detailed explanation of its purpose. The annual report also requires comprehensive data on individual employees utilizing official time, including their position, annual pay, bonuses, and the cost of benefits, as well as the total hours spent on union activities and its percentage of their total work hours. Agencies must further disclose the total compensation paid for negotiating collective bargaining agreements, processing grievances, and engaging in mediation or arbitration. The bill also seeks to quantify the value of agency resources provided to labor organizations, such as real estate, property use, and administrative support, and requires an explanation for any increase in authorized official time. To ensure accountability, the Comptroller General of the United States will conduct audits at least every four years to review the accounting practices agencies use for these reports, briefing Congress on any failures to use generally accepted accounting principles.