The links below provide information and technical guidance for Software Developers and Transmitters who are interested in developing software for the Modernized e-File (MeF) Form 1042 for Tax Year 2023. Developers and other Authorized IRS e-file Providers can find information on e-filing returns through MeF in Publication 4163 PDF and Publication 4164 PDF. Directions for Corporations required to e-file can be found through the e-file for Large and Mid-Size Corporations website. Test Scenarios for the 1042 Form Family can be found on the Modernized e-File (MeF) Assurance Testing System (ATS) page. XML Schemas, Business Rules and Release Memorandum - 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 and Production. Form 1042 Schemas and Business Rules are now distributed through the Registered User Portal and your e-services mailbox. This mailbox is part of the Secure Object Repository (SOR). Users will access their mailbox in their existing e-services account to pick up the Schemas and Business Rules packages. Instructions for accessing the SOR mailbox Tax year 2023 documents Tax Year 2023 1042 MeF Accepted Forms and Schedules PDF Tax Year 2023 1042 MeF Forms Attachment Listing XLSX Tax Year 2023 1042 MeF Return Due Dates PDF Tax Year 2023 Stylesheets: MeF Stylesheets Tax Year 2023 Known Issues and Solutions Form 1042 links to TY2023 Release Memos Version Available Date ATS Dates Production Dates Comments 2023v1.0 09/05/2023 12/17/2023 01/16/2024 Current Valid XML schemas and business rules for 1042 Modernized e-File (MeF) schemas and business rules