The following links provide information and technical guidance for Software Developers and Transmitters who are interested in developing software for the Modernized e-File (MeF) Form 1041 for tax year (TY) 2021. Included are the Extensible Markup Language (XML) Schemas, Business Rules, Release Memorandum, and specific instructions. Developers and other authorized IRS e-file providers can find information on e-filing returns through MeF in the Publication 4163 PDF and Publication 4164 PDF. Test scenarios for Form 1041 can be found on the Modernized e-File (MeF) Assurance Testing System (ATS) page. XML Schemas, Business Rules, and Release Memos - Throughout the year, multiple versions of these documents may be in use at the same time. Special attention should be paid to the Release Memo issue date and the projected start and end dates for Assurance Testing System (ATS) and Production. Tax year 2021 documents Tax year 2021 1041 MeF accepted forms and schedules PDF Tax year 2021 1041 MeF forms attachment listing XLSX Tax year 2021 1041 MeF return due dates PDF Tax year 2021 stylesheets: MeF stylesheets Tax year 2021 known issues and solutions XLSX - Revised 03/26/2024 Form 1041 links to TY2021 schemas, business rules and release memos Version Available date ATS dates Production dates Comments 2021v4.3 02/09/2023 Start: 03/05/2023 End: TBD Start: 03/19/2023 End: TBD Business Rules Changes Page dated 12/28/2023 Business Rules updates provided 07/20/2022 Schemas updates provided 02/09/2022 2021v4.2 02/10/2022 Start: 03/06/2022 End: TBD Start: 03/20/2022 End: TBD Business Rules updates provided 11/14/2022 Business Rules updates provided 06/09/2022 Business Rules updates provided 04/21/2022 2021v4.1 11/12/2021 Start: 12/12/2021 End: TBD Start: 01/07/2022 End: TBD 2021v4.0 10/14/2021 Start: 11/21/2021 End: TBD Start: 01/07/2022 End: TBD Current valid XML Schema and Business Rules for 1041 Modernized e-File (MeF) Modernized e-File (MeF) Schemas and Business Rules
