You have changed your customer's sales tax/VAT status within their Customer entry, existing Sales Orders will need to be updated via Update Customer Fields to pull through updated information
Go into the Invoice that requires to be updated
You will notice a red warning for Update next to the Customer name
In the below example, the invoice is missing VAT but the Customer record has been updated to have VAT applied:
Hover over the red warning to view pop up message explaining the warning, click [Update] to pull through updated Customer information
The VAT status has now been updated
The red UPDATE warning is no longer showing.
