OM - Different Company Codes but one Clearance Windom

Dear Friends,

my org structure has many company codes all these org units are located in different places.

exg , company code

1 - mining

2 - oil

3 - gas

4 - electricity

5 - Adminstration - hr/finance/mktg/accounts/ all adminstration departments sits in here

if a employee belonging to company code 1 wants to raise a request for OTC - order to cash, or wants to get his bills cleared from company code 5, what exactly has to be done.

well the scenario is similiar to all company codes, all transactions belonging to company codes 1,2,3,4 has to be catered by company code 5,

will any one please give me a detailed explaination of how its done is ORG management.

any assistance would be highly appreciated

Thanks

Fahad