Level playing field
Taking HMRC marking their own homework aside, I think it is a scandal that there is no level playing field with regards of service based businesses.
Small business providing a service to another business does nothing different than a big consultancy providing service to another business.
Yet, when it comes to small business when the client decides to frame the engagement is scope, so that HMRC does not come poking around, the small business becomes taxed on revenue and can't make profit from such engagement, whereas a big consultancy can.
Big corporation doing the same type of work as small business should be paying the same tax as small business.
I see no reason why when something like Infosys wins a contract, they shouldn't be paying the PAYE tax on the whole value of contract (and making no profit) like small businesses are being forced to pay.