Thank you for following up, @Gordon B.

Currently, the price rules feature is in beta testing and available in the US version of QuickBooks Online (QBO). That's why you're unable to see it on the Account and Settings page.

As of the moment, our engineers release this feature only in the United States. There is no update yet on when is it going to be available in other regions.

I've got two workarounds you can perform to complete your task. First, I'd suggest manually entering the appropriate price in the Rate column when creating an invoice. View the screenshot below for your reference. 

Second, you can look for an inventory management app that's available in your region and can integrate with QBO.

For the time being, I recommend visiting our Resource Centre so you'll stay updated on our product innovations. 

In case you need to turn on other features on the Account and Settings page, check out this link for more details: Advanced Tab.

I suggest visiting our QuickBooks Online Blog to know about the latest news and updates from QuickBooks Online.

Please let me know if you have other concerns. I'm always here to help you.