I think default VAT rate for when no VAT is showing should be exempt not Zero rated- in reality there is very few items that are actually zero rated for VAT. As a bookkeeper i spend a lot of time changing the VAT rate to exempt ion your software to show it as a purchase in box 4 of a VAT return but not as Zero rated. For example when a supplier is not VAT registered. it needs to show in box 4 as a purchase for the business, but posting this as zero rated suggests the supplier is VAT registered but charging output tax at 0% which is incorrect.