You can set up default VAT code for your sales and purchase transactions, with and without VAT. The VAT codes are used as the default if a VAT code can't be determined from the customer or supplier or analysis record.
Using the ribbon navigation style
Go to System
Click VAT Rates within the VAT ribbon
Click Defaults
Click Edit
Make the changes and click Save
Using the classic or module menus navigation style
Go to System Control
Click VAT Rates within the VAT folder
Click Defaults
Click Edit
Make the changes and click Save