If you’re on an unsupported version of macOS, your Office apps will still work but you would no longer receive any updates including security updates. What if I don't update macOS to a supported version? Learn more about the latest macOS releases. The October 2022 update (16.66) is the last build to support macOS Catalina 10.15. The September 2023 update (16.77) is the last build to support macOS Big Sur. Note that new installs of Microsoft 365 for Mac also requires macOS Monterey or later. Upgrading your operating system to macOS Monterey or later will allow Office updates to be delivered for your apps. If you continue with an older version of macOS, your Office apps will still work, but you'll no longer receive any updates including security updates. Starting with the October 2023 update (16.78) macOS Monterey or later is required to receive updates to Word, Excel, PowerPoint, Outlook, and OneNote.