Maintenance cost for outsourcing services

Hi all,

Our client buys an outsourcing service to maintain their equipment.

Period of the contract is 1 year and they will maintain every month. They will pay 50% at the beginning and 50% at the end of the period.

A maintenance plan will be created and SAP will generate maintenance order every month.

How can I record the actual cost for each maintenance order = total cost of the contract / 12

Thanks