SAP Note 12523 - Company code missing and cannot be entered

Symptom:

The company code cannot be entered in master data maintenance.
No default company code appears, either.

Cause and prerequisites

Table T001K not maintained correctly.
A valuation area is assigned to each plant in table T001W.
T001K is used to assign the valuation area a company code.
During master data maintenance, the company code is then taken
from T001K. If no entry has been made in T001K, the company code
is not filled.

Solution
Use transaction SM31 to maintain table T001K.

Key word: Company code