Can I manually add VAT amount to a bill

Hello Mick15, 

Welcome to the Community page, 

If you go into the actual bill you can manually add the vat on, if it has amounts are set at no vat then the vat box will not show, you need to change this to exclusive of tax or inclusive of tax in order for the vat box to show, to add the correct vat code on the line on the bill. Then it will calculate the amount based on the percentage, you can adjust the amount  (VAT box below subtotal) that calculates if you need to with the VAT amount.