General or core English capabilities are not enough to do well in a business environment using English.  Business English a specialization on top of general English.  With general English you have the speaking and listening skills to talk with people.  Do you have the ability to use those skills effectively in a meeting?  Can you use your writing skills to create a good agenda for the meeting.  Do you have the confidence and skills needed to chair a Steering Committee meeting with company senior executives? Do you have writing/graphics skill to create a good presentation and deliver it at a conference?  Can you write a report that will be understood by the manager of a business unit and trigger that manager to act on the recommendations?

To be effective with Business English, you need to be highly proficient in English, master a number of essential skills and have broad or deep knowledge in a variety of subjects.