Adding VAT to bills when you are not VAT registered

I'm trying your software on behalf on my employer, we are not VAT registered. I tried to follow the guide: https://www.clearbooks.co.uk/support/guides/settings-2/how-to-set-a-default-vat-rate/

To set a VAT rate but this option wasn't there, when I try and add a bill I cannot select a VAT rate. under the 'Account VAT rate ' the only selection available is 'No VAT' and I can't manually type it in at the end of the line either. Can you please tell me how to add a VAT rate for bills.