Is there a way to set up notifications if someone changes supplier bank details?

A pleasant day to you, tanya-hazelden.

You can use the Audit Log feature in QuickBooks Online (QBO). From there, you can keep track of all the activities and changes made within your company file. I'd be delighted to guide you through on how to use it:

1. Go to the Gear icon.
2. Choose Audit Log.
   
3. Click the Filter button.
4. Start filtering the following: User, Date and Events.
5. Click Apply.
   

Here's a sample screenshot of what the Audit Log would look like:

To give you more insights on how to use the Audit Log feature in QuickBooks Online, here's an article made handy for you: Use the audit log in QuickBooks Online.

You got here if you have other questions. I'm always happy to help. Stay safe and have a good one.