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;

Filing Instructions

The W-2/1099 electronic filing system for the 2018 tax year is currently under development and not accessible at this time. No registration will be required for employers or payroll agencies that have a valid Missouri Employer Withholding account.

Third party payroll agencies filing for Missouri clients, that do not have a Missouri Employer Withholding account and did not register with us last year, will need to send an email to to request an MO-W3 Submission Account. Please include the responsible person’s name, email address, and phone number in your request.

1099 Reporting

While it is not statutorily required for employers to provide their 1099 files electronically, beginning 2018 for tax year 2017, Missouri will be accepting 1099 files through the same upload process being utilized for W-2 reporting.

The Missouri 1099 Reporting Requirements and Specification Handbook is designed to be used as a companion to the Internal Revenue Service Publication 1220. The handbook highlights the special requirements of the Missouri electronic filing program.


Software developers and payroll agencies interested in testing format changes for the current year should send an email to with your company’s name and contact information for the person who will be submitting test files. We will provide you with the information for accessing and submitting a test file.