How the exact structure will be defined depends on the discussions with the client during collecting of the legal/company requirements.
Before you start customizing there is usually some blueprint document, solution proposals, delta documents etc, which you should have obtained already. In them it is explained what is the project scope and how to handle some country-specific or company-specific requirements.
If you are not sure about some details on your client's requirements for corporate reporting/tax and the business processes, it is best to ask your solution architect, legal consultants and BPLs.
The answer to how all what you ask about works, is too broad to fit into a single SCN post or even in a training course. 
Edit: A good place to start is probably TERP10. I have never attended it myself, but I have heard positive feedback from colleagues/friends who took it.
Message was edited by: Veselina Peykova