http://www.irs.gov/irm/part7/irm_07-025-023.html
In general, the type of organization exempt under IRC 501(d) is one organized for the purpose of operating a communal religious community where the members live a communal life following the tenets and teachings of the organization. All of the organization’s property is owned in community and, each member, upon leaving, the organization, is entitled to no part of the community assets. The activities often consist of farming and manufacturing. The income of the organization goes into a community treasury and is used to defray operating expenses and the cost of supporting and maintaining the members and their families. See Rev. Rul. 57– 574, 1957–2 C.B. 161
http://www.irs.gov/irm/part4/irm_04-076-029.html
Under Regulation §1.6033-2(e) and the filing instructions for Form 1065, IRC §501(d) organization is required to file a partnership return on Form 1065. Even though exempt from income tax, an IRC 501(d) organization must compute "taxable income" in order to determine the amounts its members will include in their gross incomes. A religious or apostolic organization must figure its taxable income on an attachment to Form 1065 in the same manner as a corporation. Form 1120 U. S. Corporation Income Tax Return, may be used for this purpose.