Section 143.591, RSMo, requires employers with 250 or more employees to submit the Form MO W-3 and accompanying Form W-2's electronically;
- The file must follow the Social Security Administration's EFW2 format along with Missouri modifications as outlined in the Missouri Employer Reporting of W-2's Instructions and Specifications.
- The file must be submitted by January 31.
- The W-2 or 1099 data file can have any name, but must have a .txt extension.
- ZIP, Excel, and PDF are not accepted file types.
- When you submit a file, you will receive a confirmation number. Keep this confirmation number for your records.
- For additional information, visit our W-2 Electronic Filing page.
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