Definition:
Dunning is a reminder to the customer or vendor to make payment on outstanding invoices. It typically consists of a letter that summarizes the invoices that are past due and politely requests payment to be made. When you customize dunning you have to create dunning area like at what level you want to use the dunning, like business area level or company code level. After that you have to make settings for dunning procedure, in that you have to define no of due dates and no of dunning levels. there are maximum 9 levels are there.