If you have a reservation in which there is supposed to be no VAT applied (i.e.: reservation for government official person), you can achieve this in 2 steps.
STEP 1: Create up a 0% VAT rate
Make sure the rate is Private! Then in the Tax rate field select 0%.
STEP 2: Go to the reservation and change it to the 0% VAT rate
Please keep the box Keep old price checked!! Then the rate will remain the same but the VAT will be 0% :)
Learn more about rates 🤓