Hello Nicholls-Paul. Yes, you can do a 100 percent VAT transaction. To do this, click on the + sign and select the transaction type that you need so in this case expense
One the first line of the transaction, choose the account you want to use. For the rate, enter £1, and for the VAT code, select the 20% Standard code.
On the second line, select the same account. For the rate, enter -£1, and choose an Exempt code.
The total of the invoice will be 0. You can then edit the amount in the VAT box to whatever you need it to be so the full amount in this case. Any questions on this please just reply here.