Diagnosis
The selected Excise invoice document does not have a folio in RG23D.This could be because Folio generation is not active in the excisegroup mentioned.

System Response
You cannot create additional entries for Differential duty if the RG23Dregister is not maintained folio wise,.

Procedure
Please activate Folio number generation in CIN IMG Also maintain thenumber ranges for Folio number generation. This will make futureAdditional duty entry possible.