Dunning is the process which a company communicates with customers who have overdue balances or unpaid amounts. It’s essentially how your company goes about handling collection letters and other communication to make sure accounts receivable stays on track.
In SAP Business One you can set different letters to be sent to the customer depending on how far past due a payment is. The letters may start out as a simple friendly remind and progress to a legal letter. Inside SAP the system keeps track of what dunning level the customer is, and that indicates which letter has been issues last to the customer.