Normal and one time customer or vendor account is a concept of sap. In business there can be customers or vendors with whom you rarely do business. It can be defined in sap as a one time customer or vendor account. Other than this, what ever customer and vendor master you create in sap will be called as a normal account.
Unlike normal account one time customer and vendor master does not contain any customer or vendor specific information as its used for more than one customer and vendor account. Field status related to these specific master data information in an a/c group has to be suppressed or hidden by which no one can enter anything to these fields.
While posting a document for one time customer and vendor you enter customer and vendor specific data which are not done for normal accounts.
After its creation you can post transaction to record your all receivables and payable. These master records will keep all the a/cs receivable and payable data for all one time account.
To create an one time customer or vendor a/c, you need to assign it to an a/c group that has been specifically created for it. Sap has delivered a default one time vendor and customer account group, which can be used by anyone or you can create another by copying it. All other normal accounts should be assigned to a normal account group. If after some transaction, you find a one time customer or vendor is doing regular business with you then at that time you can create its master record by assigning a normal a/c group to it.
Customer and vendor accounts are maintained for each and every company code based on its business requirements. There can be clients with whom you will be doing frequent business and with some others you don’t or you do yearly once. For each master record, sap takes some storage space which can be avoided by not maintaining unnecessary master records.