The Form 990 General Instructions state, in Section J, that only certain types of attachments are permitted. Why are these permitted but others are not? The Form 990 was redesigned, in part, to promote uniform reporting and to provide a structured format for attaching information to the Form. Schedule O PDF was designed to be the mechanism for reporting any information that does not fit on the core form or the other schedules. Only the following additional documents may be included as attachments to the Form 990: name change amendment to organizing document, as required by Item B in the Form 990 heading; list of subordinate organizations included in a group return, as required by the instructions to item H in the Form 990 heading; articles of merger or dissolution, resolutions, and plans of liquidation or merger, as required by Schedule N PDF; reasonable cause explanation for a delinquent return; and a copy of the most recent audited financial statements of a hospital organization that files Schedule H PDF (Form 990), Hospitals. Note: A reasonable cause explanation for a late-filed return must be made in a separate attachment, rather than in Schedule O, because such explanation would be publicly disclosed if included in Schedule O. The documents are permitted as attachments, outside of Schedule O, because they are either separate documents that can only be provided by attaching a photocopy or a PDF file, or they must be provided separately so they can be processed by the IRS (e.g., list of group return affiliates or reasonable cause explanation for a delinquent return).