Sunlight for Unaccountable Non-profits Act or the SUN Act This bill expands the disclosure requirements for certain tax-exempt organizations. It requires (1) the annual tax return information for tax-exempt organizations and deferred compensation plans to be made available to the public at no charge and in an open structured data format that is processable by computers, with the information easy to find, access, reuse, and download in bulk; and (2) the disclosure of the names and addresses of contributors of $5,000 or more to tax-exempt organizations that participate or intervene in political campaigns on behalf of, or in opposition to, any candidate for public office. The Internal Revenue Service may withhold from public inspection any Social Security account number included on Form 990 (information returns for tax-exempt organizations).