Clearing 
Purpose
The SAP System offers the following procedures for accounts with open item management :
Integration
In one clearing transaction, you can process several accounts, different account types (G/L account, customer, vendor), and accounts from several company codes.
Features
The clearing program carries out automatic clearing within the SAP System. However, all prerequisites for clearing open items in the SAP System must be fulfilled.
Note
Customer and vendor accounts are always managed on an open item basis. For G/L accounts, however, you have to set the open item management option in their master record yourself. Open item management is recommended for the following G/L accounts:
Check clearing accounts (bank clearing accounts)
Goods receipt/invoice receipt. (See the Materials Management documentation in the SAP Library for more information on these accounts.)
Payroll clearing accounts. (See the Personnel Administration and Payroll documentation in the SAP Library for more information on these accounts.)
During clearing, the system enters a clearing document number and the clearing date in these items. In this way, invoices in a vendor account are indicated as paid, and items in a bank clearing account are indicated as cleared.
Constraints
The program does not clear special G/L transactions, or post any new documents. It therefore does not clear items if additional postings would be required.
Example
You have posted a vendor invoice. This item could be cleared with a credit memo. At the time of clearing, cash discount would have to be posted. Therefore, the clearing program cannot clear the item.
Items that require an additional posting are, for example:
Items that contain cash discount. Cash discount would have to be posted for these items.
Items that were posted using the net procedure. Cash discount clearing would have to be posted for these items.
Items that would require a withholding tax posting.
A posting would also be required if the items balance to zero in document currency, but not in the local currency or parallel currency (group or global company currency, and so on). Clearing could not be carried out in this case either.