SAP Message >6808 - Incoming correspondence already exists for period &2 in year &3

Diagnosis
For business partner &V4& you want to create incoming correspondencewith a frequency &V1& in period &V2& and year &V3&.Incoming correspondencealready exists for this business partner for this settlement period.
The incoming correspondence is reflected as an entry in thecorrespondence history with a dunning status that permitscorrespondence dunning.

System Response
No incoming correspondence is created.