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Billing 
To carry out Usage-Based Billing, the system requires usage data for usage billing. This involves the usage volume that the system determines from the volume document.
The billing document for a pool contract consists of two item levels. The item in the first level comes from the billing request item of the pool contract. The items in the second level come from the redistribution items of the single contracts involved in pool prebilling. In addition, when aggregate contracts are involved, the system adds the regular usage billing request items from the single contracts at the second level.
1. From the SAP Easy Access menu, choose Billing ® Maintain Billing Due List.
2. Enter the transaction number of the contract.
3. Choose Execute.
The system displays the billing due list for this contract.
4. Select the billing request items and start billing.