Sunlight for Unaccountable Non-profits Act or the SUN Act

Amends the Internal Revenue Code to require: (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.

Authorizes the Internal Revenue Service to withhold from public inspection any social security account number included on the information return of a tax-exempt organization (i.e., Form 990).