Thanks for joining the thread, Duncano. Let me help you out in resolving the issue with the footer, total balance, sub total and VAT balance not showing any value on your invoices.

First, I'd like to ask if this is happening to all your sales forms or if there is any error message prompting on the screen when you try to input the values on your forms. Any further details and screenshots will greatly help us narrow down the solutions to your concern. 

In the meantime, ensure that your sales tax rate is properly set up as well as the Tax box being ticked when creating your invoices so that your tax values are properly applied. Here's how to add a tax rate and agency:

1. Go to Taxes, then select Sales tax.
2. Under the Related Tasks list on the right, select Add/edit tax rates and agencies.
3. Click New and choose either a single or a combined tax rate.
4. Enter a name for the tax agency you pay, and the percentage for the rate. Use a single rate if you pay just one rate to a single agency.
5. Select Save.

You can find more information about setting up sales tax on this article. Feel free to check it out: Set up your sales tax in QuickBooks Online.

On the other hand, if the footer on your invoices are not showing on the form, ensure that it is properly customized. Follow these steps to customize them:

1. Go to Settings. Under your company, click Custom form Styles.
2. Choose the specific template and click Edit. 
3. Select the Content column and click the last part of the form.
4. Here you can edit or Add a footer text. 
5. Once everything is complete, select Done.

Feel free to refer to these screenshots for a visual guide:

If you've tried the options above and it the issue persists, open your account in an incognito browser and repeat the steps. If this works, then the issue lies on your regular browser. You'll want to clear your regular browser cache to refresh it. 

Furthermore, I'd like to share this informative article about receiving payments in QBO after sending your invoices: Receive and process payments in QuickBooks Online with QuickBooks Payments.

Please don't hesitate to come back to this thread for additional assistance about issues with the footer, sub total and VAT balance in QBO. You can tag me in your comments and I'll be glad to help you again.