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Electronic Data Interchange (EDI) Registration and Testing

EDI Registration and testing required

The Mississippi Division of Medicaid (DOM) is in the process of implementing a new Medicaid Management Information System (MMIS) – which will include a new Provider Portal – known as MESA: Medicaid Enterprise System Assistance. The new system, going live at the beginning of October, is being developed by Gainwell Technologies.

Covered entities contracted with DOM and currently submitting electronic data transactions to DOM function as trading partners. Trading partners include Medicaid-enrolled providers, clearing houses and coordinated care organizations). Any trading partner currently submitting electronic data transactions to DOM, whether a provider or a billing services vender on behalf of a provider, will soon submit those transactions using the new system, MESA.*

In preparation for go-live, each trading partner must undergo Electronic Data Interchange (EDI) registration and testing – via the new Provider Portal – to ensure the integrity of electronic transactions. This is a critical step that ties directly to the foundation of DOM’s mission. The secure transmission of electronic information is essential for accurate and timely billing, reimbursing for needed services, determining eligibility with real-time precision, and safeguarding the protected data of DOM members as well as providers.

EDI testing is now underway, and trading partners are asked to register as soon as possible to be able to test EDI submissions to MESA.

What you need to do:

Follow the steps outlined in the Enrollment and Testing Guidelines below, which contain detailed Gainwell instructions on how to enroll as a Trading Partner in the MESA system and set up your account:

Enrollment and Testing Guidelines

These instructions can also be found on the Electronic Data Interchange (EDI) Technical Documents page at

DOM Companion Guides

To help you prepare for testing, DOM Companion Guides are now available, which describe the specific technical and procedural requirements for interfaces between DOM and its trading partners. You will have an opportunity to review those companion guides with Gainwell’s technical experts.

If you any questions as you follow the steps for enrollment and registration, please contact Gainwell’s EDI team:

PRP-100 (Computer-Based Training) Provider Portal Overview

Access the PRP-100 training course for an overview of the features and functions of the MESA Provider Portal. This training will aid registration, and initial portal navigation. The PRP-100 training course is accessible through the MESA Learning Management System (LMS). Click here and follow the instructions to log into the LMS, as well as a workshop schedule for upcoming training webinars.

You can also view additional MESA information on our website, including FAQs about our transition to our new MMIS. We will update this resource on a regular basis. Please check back frequently!


*This does not apply to CHIP-only providers, as coordinated care organizations currently submit electronic data transactions on their behalf.