Stack Exchange network consists of 183 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers.
Q&A for work
Connect and share knowledge within a single location that is structured and easy to search.
The question mainly concerns business where you would "refer/recommend someone to a new client." I wonder how similarly they can be used.
Referring someone is simply directing a person's attention to another person without mentioning any qualifications.
Recommending someone is saying that the person has a good rating.
Required, but never shown