The amount of VAT calculated on certain invoices is off by a few pence, why is that?

Thanks for posting here, @Fausto,

I can share some more details about this VAT question you have for us.

There are instances that due to different rule in rounding by QuickBooks Online, the 1 penny is always left off. To resolve this, you can always override the amount for tax to match up the 1 cent.

The rounding for sales tax calculations is designed for 2 decimal place precision in QBO. So when inputting numbers, you need to take this rounding into account.

You can also adjust your VAT Liability for past invoices, but this option must be supervised by an accounting professional. Here's how:

1. From the Taxes menu, select VAT.
2. Click on Prepare VAT then pick Adjust.
3. Enter the Adjustment Date and VAT Rate.
4. Pick the Adjustment Account ▼ drop-down menu and choose an account.
5. Add the amount of the adjustment.
6. Add a memo to describe the adjustment then press Save.

I'm enclosing this article to help you manage your VAT in QBO: VAT: Getting Started

You can also reach out to our Support Team for tax corrections like this. To get in touch with our representatives, follow the steps below:

1. Go to the (?) Help menu to open the QB Assistant box.
2. On the page, enter Contact Support.
3. Pick Live Chat to connect with our live representative.
   
4. Once done, click the Live Chat link provided in the pop-up box.
   
5. On the next page, enter VAT then Let's Talk.
6. Lastly, select Start a chat.

If you have any questions about this or anything else in QuickBooks, let me know in the comment. I'll be right here to help any time. Have a lovely week!