A family of Microsoft spreadsheet software with tools for analyzing, charting, and communicating data.
To answer your main question directly, no, you are not required to purchase Excel every year. Microsoft still offers one-time purchases, including Office Home 2024 and standalone Excel, without a recurring subscription. Since you originally purchased Office in 2017 and subsequently transferred it to your Mac, I suspect the problem may involve an older Office installation or a licensing compatibility issue rather than a new requirement to pay annually. Microsoft recently documented that, starting July 13, 2026, certain older Mac and Office configurations may stop allowing users to edit or save documents. Could you please select Apple menu > About This Mac and let me know your macOS version?
One additional possibility is that Excel was installed through the Mac App Store, which requires a Microsoft 365 subscription for editing and does not recognize older one-time Office licenses.
If you have a compatible one-time license, the appropriate Office version must be installed directly from Microsoft instead.
However, before reinstalling anything, I recommend checking the version and license information first to avoid losing access to your existing installation. You can also review Microsoft's instructions for updating older Mac installations here:
https://support.microsoft.com/en-us/office/lifecycle/officeinstall/update-m365-office-macos-ios.
Since you already started a trial, please check https://account.microsoft.com/services to verify its expiration date and recurring billing status so you are not charged unexpectedly.