Hi -perfectawnings-,
Thanks for joining us here on the Community. :waving_hand:
You should see a 'No VAT' option on the drop-down which you can use here - once you set this code for one transaction a pop-up should appear asking if you want to set this as the default code for all bank transactions.
It's also worth checking that the default tax rate is set to 'No VAT' within the settings by going to the Cogwheel > Account & settings > Advanced > Accounting, so that when you enter a transaction manually this will also default to no VAT.
Please get back to us below if you have any questions!