Calculation Procedure 
The calculation procedure is central to financial mathematics calculation. You use this procedure to define the sequence in which calculations are performed across different financing views and using different calculation types (such as calculation of the lease installment payment or of the interest rate). You can define any number of calculation procedures and calculation sequences in Customizing.
SAP provides the following calculation procedures:
FM_001 - Calculate Payment Amount
FM_002 - Calculate Nominal Interest
FM_003 - Calculate Amount Financed
FM_009 - Calculate Cash Flow
No calculations are performed in this procedure.
Prerequisites
You have performed all the activities in Customizing for SAP Customer Relationship Management (SAP CRM) by choosing 
Customer Relationship Management 
Financial Services Leasing Financial Mathematics Settings Configure FIMA Calculation Procedure 
.
Activities
In the master data of the financing product, you select the required calculation procedure and assign it to a pricing process and, if necessary, to a sub-pricing process. You can assign any number of calculation procedures for each pricing process in the master data of the product. In doing so, you must select one calculation procedure as Default. The system automatically suggests this procedure in the quotation. However, you can select a different calculation procedure manually.
Note
You must have defined a calculation procedure for the New Lease (NEWL) business transaction. This calculation procedure is copied to all follow-on processes, unless you assign a different calculation procedure to the follow-on process in the product master data.