Attention: Software Developers, Return Transmitters and Authorized IRS e-file Providers/EROs.

As part of ongoing efforts to strengthen fraud detection and security across the e-file ecosystem, the IRS is implementing secure Application Program Interfaces (APIs), including real-time Electronic Filing Identification Number (EFIN) Validation and Vendor Control Number (VCN) Registration services.

These APIs are designed to simplify and streamline the registration process for e-file software developers. They allow software companies to validate EFIN ownership and status and pre-register e-file software, by Software ID, under the company's VCN before electronic returns are submitted through Modernized e-File (MeF). Software companies and states may register for access, complete integration and begin testing starting August 16, 2026.

To support registration and integration, the API specification documentation has been distributed to users through their e-Services mailbox. This documentation is required to integrate with and call the APIs, helping ensure a smooth onboarding experience. 

We are targeting a tentative production deployment date of September 1, 2026.

If you have any questions, please send them to the MeF mailbox at: mefmailbox@irs.gov.