SAP is marketed as a fully integrated system, therefore knowing some of the integration points enables the Users to better understand the Modules.
Organization units are not only defined in FI(Financial Accounting) but also in other SAP Modules. The SD( Sales & Distribution) Module requires the set-up of Sales Organizations, Distribution Channels and Divisions ; Purchasing requires purchasing organizations, plants, and storage locations; and CO (Controlling) requires a Controlling area to be defined.
To transfer data between FI(Financial Accounting) and CO (controlling) as well as other modules, a Company Code must be assigned to each of the Modules.
Business Areas must be entered when generating business transactions if you would like visibility of those transactions impacting a certain BA(Business Area). You can also update your Master Records to include BA(Business Area) for example Cost Center.
Document postings are automatically posted in the year and periods that you created in the Fiscal Year variant set-ups based on the month, start and end dates to which postings are allowed within a given period as defined.
There are several integration points in SAP, the above lists a few .