Can you tell us what you've seen on your end when trying to adjust the VAT return?
You can check the Manage Users section to verify if you have the correct role to adjust the VAT return.
If you do have the right role but the system still prevents you from making adjustments, try refreshing the page. You might also want to log out and then log back in to see if that improves performance.
Additionally, you can edit your VAT amount using the Journal Entry.
Click on the incorrect VAT amount > Journal Entry > correct the amount > Save.
Once saved, the Box 6 in your VAT will have the updated amount.
You can always reply or reach out to us again if you need anything else with VAT or any QBO-related tasks. We're always here to guide and assist you whenever you need help.