This guide is for Microsoft Office 2021 Professional Plus for Windows, which includes Word, Excel, PowerPoint, Outlook, OneNote, Access and Publisher 2021.
Before you start
- Office 2021 requires Windows 10 or Windows 11. It will not install on Windows 7 or 8.1.
- 4 GB RAM, 4 GB free disk space and an internet connection.
- Have the 25-character product key from your delivery email ready.
- Microsoft support for Office 2021 ends on 13 October 2026. The apps keep working after that, but security updates stop.
Step 1: Remove any existing Office
- Open Settings > Apps > Installed apps.
- Uninstall every Microsoft Office or Microsoft 365 entry, including pre-installed trials.
- If anything refuses to uninstall, use Microsoft's Office uninstall support tool.
- Restart the PC.
Step 2: Download the Office 2021 installer
Use the download link in your delivery email. It points to the official Microsoft installer for Office 2021 Professional Plus. Choose 64-bit unless a legacy add-in requires 32-bit. If you plan to add Project 2021 or Visio 2021 later, they must use the same bit version.
Step 3: Install
- Run the installer and accept the User Account Control prompt.
- Keep the PC online and awake until you see You're all set! Office is installed now.
Step 4: Activate Office 2021
- Open Word 2021.
- Choose Enter a product key instead at the prompt, or go to File > Account > Change product key.
- Enter your key and follow the prompts. Sign in with your own Microsoft account if asked, so the licence is linked to you.
- Confirm File > Account shows Product Activated: Microsoft Office Professional Plus 2021.
If your delivery email states your key uses phone activation, select I want to activate the software by telephone in the wizard.
Office 2021 specific problems
Key rejected as "for a different version"
You installed a 2024 or 2019 installer. Only the Office 2021 installer accepts a 2021 key.
Error 30015 or 30088 during install
Leftover files from a previous Office. Repeat Step 1 with the uninstall support tool.
"This app can't run on your PC"
The PC is on Windows 7 or 8.1. Office 2021 needs Windows 10 or 11; there is no workaround.
XLOOKUP or dynamic arrays missing in Excel
You are running an older Excel build. Go to File > Account > Update Options > Update Now.
Need help?
Stop retrying a rejected key. Screenshot the error and contact support with your order number. Your purchase is covered by our 6-month licence warranty.