Payment for demand might already be collected fully or partly by previous payment or system
Solutions
Check existing demand on HLAOPI first.
1. If demand exists and collection has been made in full by the system, then transfer the payment to Income.
2. If demand exists and collection has been made partly by the system, then pay the existing non-collected demand on HLASPAY and transfer the remaing amount to Income. You may check how much is allowed for payment on the breakdown of Principal and Interest on the lower part of HLASPAY.