Ledger needed for customer/site definition ?

 Hi,We are starting with a new implementation and as part of that initially we just need to load the customer master data in that. The question is , do we really need to define the ledgers/document sequences for loading the customer data or for creation of customer sites.We are not planning to create any transactions at this point. 

I believe only the operating unit defn is sufficient,  for the customer sites. Is there any place in the customer setting where we need to define an account and hence the ledger definition is mandatory.

Any thoughts on this,

Thanks,Lakshmi.