How do I enter a gift voucher?

According to my accountant, I should not enter gift vouchers under receipts because they have 0% vAT. But I do have to put them in a separate Excel file to keep track of them. The accountant will process this later. But I find this so cumbersome.

Is there really no way to enter the gift vouchers sold immediately? And how do I enter it correctly when a gift voucher has been redeemed?
E.g.: Customer has to pay £100 and gives a voucher from £50. Do I only enter that £50 because the gift voucher was entered earlier?

Best regards!