The typical format/structure of a business report is:
Executive summary - this is almost like an introduction that should set the context of your response and outline exactly the direction you intend to take your response in.
Various body paragraphs (using headings and diagrams and tables etc to illustrate your points) - I would recommend that you set it out based on the key components of the question, using headings to separate it all out.
Recommendations/Conclusion - this is self-explanatory, try to tie everything together, and if you are making recommendations, you can either do it here at the end or make your recommendations throughout the body of your response.
Business reports are compulsory for Section 3 of the HSC exam - however, in Section 4, you are able to use any format that allows you to express your ideas clearly and thoroughly. Most students will typically adhere to the business report style for Section 4 because it does give you that extra flexibility in the way that you present your ideas and does give you the opportunity to be less formal in your approach. However, if you are a strong writer with very well-developed essay writing skills, I would recommend that you use an essay style for Section 4. I attended a Selective high School and my Business Studies teacher encouraged everyone to use a Business Report format for Section 4, but I was never really a fan of business reports as I was a strong essay writer, so I eventually was the only student in my cohort that wrote in essay format. I preferred that because often the questions are worded in such a way that it is difficult to flesh it out in a business report, as you need to use diagrams, tables and other illustrations to support your response, and I thought it would be more effective if I used an essay. At the end of the day, you should be really careful how you present it, as you don't want to make it unclear to the marker, and a business report has the advantage that it does make it easier for the marker, which may help in creating a more positive impression of your exam response.
Hope this helps!!!