This is a handy transaction to do a high-level check of the configuration associated with certain configuration objects like company codes or plants.
Because the configuration required for new company codes, sales orgs, etc. depend on how your organization runs its business, so it's hard to know which configuration ("T") tables need to be updated to properly configure, say, a new company code. (For example, if your company doesn't use intercompany balance transfers, you won't need to add entries to the intercompany relationships table T001U).
A good baseline to see which configuration tables are used/supported at your organization is to run transaction EC01 (EC-zero-1) in your configuration client.
Select the "Check Org Object" option (F8), and enter a company code you know to be correctly configured. This will run a program that checks for the presence of a given company code value in each of about 100+ "T" tables in the system. You can run EC01 for an existing company code configured in your system and see which tables have entries for this company, and work backward from the table names to determine what configuration you should add. Transaction EC02 checks tables for plants, EC03 for controlling areas, EC04 for Sales Orgs, EC05 for distribution channel, EC06 for divisions, EC07 for shipping points, EC08 for chart of depreciation, EC09 for warehouse number, ...
You can download the displayed results to a local excel file, and compare the table entries between existing companies (sales orgs, plants, etc).