Welcome and thanks for reaching out to the Community, @sales.tyrecarece.
Are you getting any error messages when trying to add a GST tax rate in QuickBooks Online (QBO)? Any additional information will help me provide the best resolution.
In the meantime, I suggest signing in to your QBO using a private browser (incognito). This will help us check if this is a browser-related (cache and cookies) issue.
Here's how:
Press Ctrl + Shift + N (Google Chrome).
Ctrl + Shift + P (Firefox).
Control + Option + P (Safari).
Once signed in, create a non-inventory item and try to add a GST tax rate again to double-check.
If it's successful, go back to your default browser and perform a clear cache to refresh the system. However, if the issue persists, try using other supported browsers.
To learn more about setting up and managing GST in QBO, consider checking out these articles for future reference: