There two things one should consider while creating legal entities
1. The number of fisical and tax report the organization has to produces – for each distinct values we should create one legal entity.
2. The number of entities for which the company produce balance sheet – for each distinct values we should create one legal entity.
OU deals with 5 subledgers – OM, AR, PO, AP and GL
Security and Subledgers decides how many operating units one should create in a business group.