Spotlight Act This bill repeals an Internal Revenue Service (IRS) revenue procedure (Rev. Proc. 2018-38) that exempts certain tax-exempt organizations that are not 501(c)(3) organizations from the requirement to report the names and addresses of substantial contributors (persons who contribute more than $5,000 per year) on information returns that are filed with the IRS. The bill requires tax-exempt organizations that fall under sections 501(c)(4), 501(c)(5), and 501(c)(6) of the Internal Revenue Code (e.g., social welfare organizations, labor organizations, business leagues) to disclose the names and addresses of all substantial contributors on their returns. The information must also be made available to the public. The bill also eliminates the authority of the IRS to provide exceptions to the disclosure requirements for tax-exempt organizations. This provision does not apply to determinations made by the IRS before July 16, 2018.