SAP Message TU503 - Cannot find schedule record in portion &1 for start month/yr (&2/&3)

Diagnosis
You tried to create a payment plan with start month &V2& and start yearV3. however, no schedule records have been created for portion v1.

System Response
You cannot create the payment plan.

Procedure
Create schedule records for the portion and the meter reading unit thatbelongs to it.