Office 2021 loses security support on 13 October

What end of support actually means

Office 2021 uses Microsoft’s Fixed Lifecycle Policy. Its support end date was set when the product was released. Microsoft states that after 13 October 2026 it will not provide technical support, bug fixes or security updates for Office LTSC 2021. Microsoft Support also states that there is no extension and no Extended Security Update programme for Office 2021.

Word, Excel, PowerPoint and Outlook may still open after the deadline. That does not make the environment supported. New vulnerabilities can remain unpatched. Reliability defects can remain unresolved. If a business application, add-in or document behaves incorrectly, Microsoft support is no longer available for the affected Office version.

The same date matters for connections to Microsoft 365 services. Office LTSC 2021 is supported for connecting to Exchange Online, SharePoint Online and OneDrive until 13 October 2026. Older clients may continue to connect after their supported date, but Microsoft does not test service improvements against them and warns that functionality, performance or reliability can change unexpectedly.

Why a device count is not enough

A simple count of Office 2021 installations shows scale, not migration risk. Two devices running the same version can carry very different consequences. A standard knowledge worker may need only a controlled application upgrade. A finance workstation may run signed macros, specialist Excel add-ins and month-end templates. A production device may have limited connectivity or depend on a validated process.

The useful inventory links the installation to its device, user, operating system, edition, bitness, Project or Visio dependency, update channel, add-ins, macros, automation and business criticality. It also records whether the device connects to Microsoft 365 services and whether the user’s licence includes desktop applications.

Start with the highest-consequence groups: finance, executive support, shared operational workstations, users with complex spreadsheets, devices with COM or web add-ins, and processes that generate regulated or customer-facing documents. These groups need evidence from a pilot, not an assumption that a newer version behaves the same.

Choose the target by operating model

Microsoft recommends moving to Microsoft 365 Apps. This is the continuously serviced desktop Office product included in eligible Microsoft 365 plans. It receives security, quality and feature updates while the organisation remains on a supported version and update channel.

Microsoft recommends Office LTSC 2024 where an on-premises commercial release is required. Office LTSC 2024 follows a fixed lifecycle and reaches end of support in October 2029. It receives security and quality updates but does not receive ongoing new Office features.

The choice should follow the device’s real constraints. Microsoft 365 Apps is usually the better fit for connected users who need current Microsoft 365 integration and regular improvements. Office LTSC 2024 may suit defined scenarios where devices need a fixed feature set, have restricted connectivity or operate under a controlled validation process.

Do not make a tenant-wide decision from one exception. Segment the estate. Most users may move to Microsoft 365 Apps while a smaller, documented group follows the LTSC path. The exception group still needs a support end date, licence position and review owner.

What must be tested before deployment

Microsoft’s upgrade guidance calls out Visual Basic for Applications scripts, macros, non-Microsoft add-ins, complex documents and spreadsheets. These are the places where a technically successful installation can still cause a business failure.

A representative pilot must cover the work people actually perform. Open and save core templates. Refresh data connections. Run macros. Produce PDFs. Test mail merge. Confirm Outlook profiles and shared mailboxes. Validate add-ins, printing and document management integration. Include both routine work and known exceptions.

Use the existing deployment method where possible. Microsoft’s Office Deployment Tool can download and deploy Microsoft 365 Apps through the organisation’s standard software distribution process. Confirm update channels, architecture and application exclusions before broad deployment. Project and Visio require separate attention because licensing and channels can differ from the core Office suite.

Decision owner

Primary owner: The endpoint or workplace platform lead owns the estate and deployment. Application owners prove specialist workflows. Procurement confirms licensing. Security and compliance approve temporary exceptions. Business owners sign off the pilot result.

Action within seven days

1. Day 1: Export Office 2021 installations with device, user, edition, operating system and last activity.
2. Day 2: Add Project, Visio, bitness, update channel, macros, add-ins and business process information.
3. Day 3: Segment users into standard, specialist, restricted-connectivity and regulated groups.
4. Day 4: Choose Microsoft 365 Apps or Office LTSC 2024 for each group and confirm licensing.
5. Day 5: Build a pilot group containing standard users and the highest-risk specialist workflows.
6. Day 6: Run the test script, log defects and confirm rollback, service-desk and communication plans.
7. Day 7: Approve the deployment waves and record every temporary exception with an owner and expiry date.

Evidence to retain

• The dated Office 2021 installation inventory with device and accountable owner.
• The target-product and licence decision for every user segment.
• Pilot evidence for macros, add-ins, complex documents, printing and line-of-business integrations.
• The deployment configuration, update channel, application exclusions and rollback package.
• The user communication, service-desk knowledge article and defect log.
• The migration schedule and approved exception register with expiry dates.

Questions decision-makers are asking

Will Office 2021 stop opening after 13 October 2026?

Microsoft does not say the applications will be disabled. They can continue to run, but security updates, bug fixes and technical support end. Continuing to use them transfers the risk of new vulnerabilities, defects and compatibility problems to the organisation.

Can we buy extended security updates for Office 2021?

No. Microsoft Support states there will be no extension and no Extended Security Updates for Office 2021. Organisations need to move to a supported product or carry a formally approved exception with compensating controls until migration is complete.

Is Microsoft 365 Apps the only replacement?

No. Microsoft recommends Microsoft 365 Apps for a continuously supported environment. Where a subscription or connected operating model is unsuitable, Microsoft identifies Office LTSC 2024 as the current supported on-premises commercial release. The right answer can differ by device group.

What should we test first?

Start with work that can stop a business process: finance macros, specialist Excel add-ins, document templates, data connections, mail merge, PDF output, Outlook integrations, Project and Visio. A representative pilot should prove outcomes, not only confirm that the applications launch.

The Braintree view

This is an estate-management decision, not a licence-renewal task. The safest plan separates ordinary users from exception devices, proves critical workflows and gives each remaining Office 2021 installation a named owner and removal date.

Use the Braintree Briefing episode to align the deadline across IT, security, procurement and business owners, then speak to a Braintree specialist to define the inventory, target groups and pilot.