I will provide some snapshots for a clear picture.
Late Fee process:
Note the material used is LATE_Fee. It has fixed charge 100 DKK if the customer has not paid the invoice after due date.
Note the condition type ZLLF used to hold the value of 100 DKK and MWST for output tax.The value 100 DKK is based on the dunning level of the customer and is stored in FBMP T code as shown below.
Interest charge process:
Note the INTERES_CHRG material and the value. This value is derived from the value of original invoice (Which is already paid by customer after due date) X No of days it is paid after due date X interest percentage %. This calculation is automatically done by SAP through FINT T code. We just got the value from FINT and provided it in order, condition type ZLFE.
Interest percentage are stored based on interest indicators in OB42 T Code as shown below.
Mention this interest indicator (Z1) in customer master>Company code view->Account management tab->Interest indic.
The order creation is done by program which runs as batch job. and billing takes place as per usual standard billing job.
Thanks
Dattatreya N R