Microsoft 365 GCC High Migration for Government Contractors

Microsoft 365 GCC High migration is the process of migrating files, emails, libraries, chat data, and identity infrastructure from a non-compliant environment to Microsoft’s sovereign government cloud, built specifically for defense contractors handling Controlled Unclassified Information (CUI), ITAR-regulated data, and DoW (Department of War; formerly DoD: Department of Defense) contracts.

If your organization holds a DFARS 7012 clause or is pursuing CMMC Level 2 certification, migrating to Microsoft 365 GCC High is a must!

This guide walks you through everything you need to know about Microsoft 365 GCC High migration, including:

• What it is
• Why it’s important
• Why it is urgent
• The process
• Timeline, and more

What is Microsoft 365 GCC High?

Microsoft 365 GCC High is a sovereign cloud built on Azure Government infrastructure. It is intended exclusively for the US Defense Industrial Base (DIB) and organizations handling sensitive federal data.

As compared to the standard Microsoft 365, GCC High:

• Stores all data exclusively in US-based data centers.
• Meets FedRAMP High, DFARS 7012, ITAR, EAR, and CMMC Level 2 and 3 requirements.
• Fully isolated from commercial cloud servers.
• Restrict access to screened persons only.

The productivity suite is the same. It includes OneDrive, SharePoint, Outlook, Teams, and other Microsoft tools. The difference lies in the security of the infrastructure it runs on.

Who Needs to Migrate to GCC High, And Why?

Any US organization that handles Controlled Unclassified Information (CUI) under a DoW contract benefits from migrating to Office 365 GCC High.
More specifically, GCC High is strongly recommended for:

• Defense contractors and subcontractors holding DFARS 252.204-7012 clauses.
• Aerospace and defense manufacturers handling ITAR or EAR export-controlled technical data.
• Federal agencies and cabinet-level organizations that require DoW IL4/IL5 assurance.
• Higher education and research institutions that receive DoW funding and conducting defense-level research.

What Data Can Be Migrated to Microsoft GCC High?

The following workloads can be migrated to GCC High:

• OneDrive for Business (personal files, folder structures, metadata).
• SharePoint Online (sites, document libraries, permissions, metadata).
• Exchange Online (email, calendar, shared mailboxes, contacts, archives).
• Microsoft Teams (channels, chats, files, context).

Why It’s Urgent to Migrate

CMMC implementation for US defense contractors and DIB organizations has already started. Phase 1 began on November 10, 2025, which requires contractors to complete Level 1 and Level 2 self-assessments and submit affirmations in SPRS.

Now, Phase 2 goes live on November 10, 2026. From that date, DoW contracts will require Level 2 C3PAO certification as a condition of contract awards. Self-assessment will no longer be enough.

• Since cloud infrastructure must be compliant before an assessor can certify it, organizations without GCC High cannot complete a C3PAO certification.
• Subcontractors without the certification become ineligible to serve on the CMMC clause contracts.

Steps to Migrate to Microsoft 365 GCC High

The process of migrating to Microsoft 365 GCC High is not the same as a standard Microsoft 365 migration. Therefore, you must take proper preparation, planning, and execution steps. Here’s the entire process:

Step 1: Eligibility Validation

It is important to first be eligible for Microsoft 365 GCC High. For this, you need to submit several eligibility documents to Microsoft 365, including:

• A signed contract with a U.S. government agency that explicitly indicates a regulated data requirement.
• CAGE (Commercial and Governance Entity) Code.
• A valid SAM (System for Award Management) registration.

Step 2: Source Environment Assessment

The best way to lay a solid foundation for migration is to perform a full assessment of your current environment. Here are some of the key action items:

• Reviewing the source environment architecture (Active Directory, Google Workspace admin, on-premises directory structure, etc.).
• Third-party application and integration inventory.
• Classifying data into what is CUI and what is not.
• Identifying compliance gaps against NIST 800-171 controls.
• Documenting all team sites, shared drives, messaging channels, external collaborators, etc.

Step 3: AOS-G Partner Engagement

Since commercial Microsoft 365 licenses are not applicable to GCC High, you must purchase GCC High licenses. And to be able to do this, you must engage an AOS-G (Agreement for Online Services – Government) partner. Also, make sure to provision the new tenant.

Step 4: Rebuild Identity

Since Microsoft 365 GCC High operates on a completely separate Azure Active Directory (Microsoft Entra ID) infrastructure, your existing Entra ID configuration does not carry over. Therefore, it is important to:

• Configure identity synchronization to GCC High end points.
• Reconfigure MFA (multi-factor authentication) policies, conditional access rules, and device compliance policies.

Step 5: Pre-Migration Data Preparation

Here are some important preparation steps to take before proceeding with migration:

NOTE: Classify data to confirm CUI scopes before they are migrated. This applies to all source environments.

Step 6: Perform the Migration

A cutover migration approach is the best recommended option for almost all Microsoft 365 GCC High migrations. This is because the end goal is to move completely to GCC High and align with its US region localization.

This is where a third-party cloud migration solution like CloudFuze Migrate becomes critical. With CloudFuze Migrate, government contractors can securely migrate to Microsoft 365 GCC High, including:

• SharePoint Online
• Exchange Online
• OneDrive for Business
• Microsoft Teams

CloudFuze supports migrations to Microsoft 365 GCC High from commercial Microsoft 365 tenants, Google Workspace, on-premises environments, and other file storages that exist as secondary data sources.

Step 7: Post-Migration Validation

After migration completion, it is important to validate thoroughly. Some of the important validation action items include:

• Verify that all the planned workloads have been migrated, including files, folders, emails, chat data, libraries, and more.
• Review permissions and access policies.
• Confirm that every user has the correct GCC High license type.
• Validate third-party integrations that were configured for GCC High endpoints.

How Long Does a GCC High Migration Take?

Office 365 GCC High migration timeline varies by data size and environment complexity. Here are estimated timelines:

Other factors that shape the GCC High migration timeline include:

• The time Microsoft’s eligibility validation takes.
• The total number of third-party integrations that require reconfiguration.
• Format conversion of Google-native files.
• Directory clean up when migrating from an on-premises environment.

Post-Migration Governance

Migrating to Microsoft 365 GCC High closes the compliance gaps at the infrastructure level. However, it is equally important to close the governance gap that starts widening as usage scales across the GCC High tenant.

As usage grows, overpermissioned accounts accumulate, stale permissions of offboarded users linger, and so on.

What’s more important to note is that Microsoft 365 Copilot is now available in GCC High. This means that the risk of inadvertent sensitive data exposure to unauthorized users can be amplified. And having visibility over autonomous agents can get challenging.
CloudFuze Manage provides the governance layer government contractors need to:

• Govern content and permissions sprawl
• Govern AI agents
• Control Shadow IT and Shadow AI
• Manage user lifecycle
• Align license spend with actual usage

Understand More with a Free Migration Consultation

Want to understand more about how migrating to Microsoft 365 GCC High plays out for your organization? We would be happy to help you with a free migration consultation without any obligation. Contact us today!

Frequently Asked Questions

1. Can a foreign-owned or foreign-controlled company get access to Microsoft 365 GCC High?

No. Microsoft requires organizations to be US-based and operated to be able to access GCC High. This also means US subsidiaries of foreign parent companies are generally ineligible unless they have a Special Security Agreement (SSA).

2. Can you use Microsoft 365 GCC High and commercial Microsoft 365 simultaneously?

Yes. With an enclave approach, government contractors can have employees handling CUI operate in GCC High while the rest of the organization stays on commercial Microsoft 365. However, cross-tenant collaboration is restricted, and users cannot be in both tenants simultaneously on the same browsing session.

3. What happens if a subcontractor in your supply chain is not GCC High compliant?

Under CMMC flow-down requirements, prime contractors are responsible for ensuring that subcontractors handling CUI are also compliant. This means non-compliance risk increases for prime contractors if the subcontractors are not GCC High compliant and cannot meet CMMC Level 2 requirements.