I have just noticed that when the vat is calculated on a quote or invoice it's not taking vat from the full amount.

I appreciate you for reaching out to us, Ness. I'd be glad to provide you the steps in changing the Tax rate in your QuickBooks Online account.

Since it's not deducting the full amount of your VAT rate, I'd suggest checking your Tax settings to ensure that it's showing 23% rate.

Here's how:

1. In your QBO account, go to Taxes.
2. On the upper right corner, click Edit Sample dropdown.
3. Select Edit rates.
4. Under the Action column, click Edit. 
5. Review the Purchase rate if it's having 23%.
6. Click Save once done.
    

Furthermore, you can also check on your products if the VAT you've selected is correct.

Here's how:

1. Go to the Gear icon, then select Products and services.
2. Locate the items that you're selling,
3. Under the Action column, click Edit.
4. Click the dropdown on the Tax field.

If it's all correct, I'd suggest performing browser troubleshooting steps. Sometimes, cache-related issues can cause QuickBooks Online (QBO) to load incorrectly, preventing you from connecting with your bank.

Additionally, you can run a tax report  that helps you keep track of your sales tax liabilities and ensure timely and accurate filings.

Please feel free to post any additional questions or updates, and we’ll be happy to assist you further. Take care.