Skip to main content

Microsoft 365 is a subscription that gives you continuously updated Office apps, cloud storage, Teams, Exchange Online, and enterprise security. Office 2021 is a one-time purchase of desktop apps frozen at the 2021 feature set. For enterprises, Microsoft 365 is almost always the right choice — here is why.

Key Facts

  • Office 2021 reaches end of mainstream support in October 2026. After that, security patches only through 2026.
  • Microsoft 365 includes cloud services — Exchange Online, SharePoint, OneDrive, and Teams — that Office 2021 does not.
  • Microsoft 365 Copilot ($30/user/month add-on) requires a Microsoft 365 base license. Copilot does not work with Office 2021.
  • For enterprises planning AI deployment, Microsoft 365 E3 or E5 is the only viable path.
Back to Blog

Last updated by Errin O'Connor, Founder & Chief AI Architect, EPC Group

Errin O'Connor
8 min read

Microsoft 365 vs Office 2021: How to Choose

Key differences at a glance

Category Microsoft 365 Office 2021
Licensing model Subscription (per user/month) One-time purchase
Apps included Word, Excel, PowerPoint, Outlook, Teams, OneNote, Access Word, Excel, PowerPoint, Outlook, OneNote (no Teams)
Updates Continuous feature updates via Current Channel Security updates only (no new features)
Cloud services Exchange Online, SharePoint, OneDrive, Teams None (desktop apps only)
AI features Copilot add-on available ($30/user/month) No AI or Copilot features
Security Defender, Purview, Conditional Access, DLP No enterprise security features
Support lifecycle Ongoing (tied to subscription) End of support: October 2026
Enterprise pricing E3: $39.00/user/month · E5: $60.00/user/month (Microsoft list, annual commitment, with Teams; read 2026-10-21) ~$440/user one-time (LTSC 2021)

Microsoft 365 enterprise plans

  • Microsoft 365 Apps for Enterprise ($12/user/month) — Office apps only, no Exchange or Teams included.
  • Microsoft 365 E3 ($39.00/user/month, Microsoft list, annual commitment, with Teams; read 2026-10-21) — full suite: apps, Exchange Online, SharePoint, Teams, Intune, basic compliance.
  • Microsoft 365 E5 ($60.00/user/month, Microsoft list, same terms) — adds Defender for Endpoint P2, Purview Insider Risk, advanced compliance, Power BI Pro.

When Office 2021 still makes sense

Office 2021 (LTSC) fits a narrow set of scenarios.

  • Disconnected or air-gapped environments that cannot use cloud services.
  • Regulated systems where software version control is mandatory and continuous updates are not permitted.
  • Specialized devices (kiosks, factory floor terminals) where desktop apps are needed with no cloud connectivity.

For most enterprise users, these scenarios do not apply. If your users need email, Teams, or AI features — choose Microsoft 365.

Migrating from Office 2021 to Microsoft 365

The migration has four steps. EPC Group runs each step with minimal user disruption.

  1. Provision Microsoft 365 licenses for all users.
  2. Deploy Microsoft 365 Apps for Enterprise via Intune or Configuration Manager.
  3. Migrate email to Exchange Online (if not already there).
  4. Configure OneDrive for Business file synchronization and redirect My Documents.

Timeline: small organizations (under 500 users) typically migrate in 4–8 weeks. Enterprise migrations take 8–16 weeks with phased rollout.

Impact on security and compliance

Microsoft 365 is not just a productivity upgrade. For enterprises, it changes your security and compliance posture significantly.

  • Exchange Online adds anti-phishing, Safe Attachments, and Safe Links — not available in on-premises Exchange or Office 2021.
  • Microsoft Purview DLP, sensitivity labels, and eDiscovery require Microsoft 365 licensing.
  • Conditional Access policies in Entra ID require Microsoft 365 apps on Current Channel — not Office 2021.
  • HIPAA, SOC 2, FedRAMP, and CMMC compliance frameworks all assume Microsoft 365, not Office 2021.

Frequently asked questions

What is the main difference between Microsoft 365 and Office 2021?

Microsoft 365 is a subscription with continuously updated apps plus cloud services (Exchange Online, SharePoint, OneDrive, Teams). Office 2021 is a one-time purchase of desktop apps with no cloud services and no feature updates after release. Office 2021 reaches end of support in October 2026.

Can I use Microsoft Copilot with Office 2021?

No. Copilot for Microsoft 365 requires an active Microsoft 365 subscription (E3, E5, Business Standard, or Business Premium) plus the $30/user/month Copilot add-on. Office 2021 does not qualify and has no AI features.

Is Microsoft 365 more expensive than Office 2021?

Microsoft lists Microsoft 365 E3 at $39.00/user/month ($468/year; annual commitment, with Teams; read 2026-10-21). Office 2021 LTSC is approximately $440 per device one-time. Over three years, M365 E3 costs ~$1,404 per user (computed from the Microsoft list price) — but includes cloud services, security, and continuous updates that Office 2021 does not provide.

What happens when Office 2021 reaches end of support?

Office 2021 mainstream support ends October 2026. After that, Microsoft provides security patches only through the extended support date. No new features will be added. Organizations still on Office 2021 after 2026 face increasing security risk as vulnerabilities are discovered but not fully patched.

How long does migrating from Office 2021 to Microsoft 365 take?

Four to eight weeks for most organizations under 500 users. Enterprise migrations (1,000+ users) with email migration, SharePoint setup, and phased rollout take 8–16 weeks. EPC Group uses Intune or Configuration Manager to deploy Microsoft 365 Apps for Enterprise at scale.

Upgrade to Microsoft 365

EPC Group manages Microsoft 365 migrations for enterprises of all sizes. Call (888) 381-9725 or schedule a discovery call to plan your migration.

Related guides and articles

Microsoft 365 Strategy: 2026 Considerations for Microsoft 365 Vs Office 2021 How To Choose The Right Product

Microsoft 365 E5 vs E3 in 2026 is fundamentally a security and compliance decision. E5 (Microsoft list $60.00/user/mo, annual commitment, with Teams; read 2026-10-21) bundles Microsoft Defender for Endpoint Plan 2, Microsoft Defender for Cloud Apps, Insider Risk Management, Communication Compliance, Microsoft Sentinel-fed audit logs, Customer Lockbox, and Audit (Premium) — one-year default audit retention for Exchange, SharePoint, OneDrive and Entra ID records, with ten-year retention available only through the separately licensed 10-Year Audit Log Retention add-on (Microsoft Learn, 'Audit log retention policies', accessed 2026-10-21); the full set is roughly $35/user/mo of additional value if purchased as E3 plus add-ons. For regulated industries, the E5 bundle is typically less expensive than the equivalent E3 stack.

Microsoft 365 GCC High vs Commercial tenant in 2026 governs whether a contractor can hold Controlled Unclassified Information (CUI) for federal work under CMMC Level 2 (110 NIST 800-171 controls) or Level 3 (134 controls). GCC High costs roughly 2x the commercial equivalent (Microsoft list price $26.00-$60.00/user/mo, Office 365 E3 through Microsoft 365 E5, annual commitment, with Teams; read 2026-10-21) but is non-negotiable for any DoD prime or sub-prime handling CUI. Migration from Commercial to GCC High is a 14-22 week project.

Decision factors EPC Group evaluates

  • Customer Lockbox + Audit (Premium) configuration for regulated tenants
  • Microsoft Purview Compliance Manager assessment baseline (HIPAA, SOC 2, GDPR, NIST AI RMF)
  • E5 vs E3 + add-ons total-cost analysis at organization scale
  • Microsoft Defender for Endpoint Plan 2 deployment versus Plan 1 + add-ons
  • GCC High vs Commercial tenant decision for federal contractors

See related EPC Group services or schedule a discovery call.

AI assistant — not a human