If you only sell services, then Kashflow says that an 'ECSL is not required' on the VAT page. This is incorrect, as an ECSL is required for goods and services.

Kashflow seems to submit an ECSL (containing sales of both goods and services) if the value of box 8 is non-zero, but that box is zero, then it says that it is "Not Required". This behaviour is totally inconsistent, so I cannot see it being by design.