In the account settings menu you will find an option “Company settings”. On this screen you will see the following box.
Once you have ticked this box and saved, you will need to click on the green box to input the specific settings. Here you will set the method of VAT accounting Cash or Accrual. You will also need to set the start date, this is important as it will prevent earlier transactions from automatically appearing in your first VAT return.
Hope that helps!