Pay Bills > Select Bill and Bill Credit (Partial Amount) > "Negative Bill Payment is not allowed."

User is trying to partially pay a Bill with a Bill Credit on the Pay Bills page but is getting an error "Negative Bill Payment is not allowed."

Steps to Reproduce:
1. Go to Transactions > Payables > Pay Bills.
2. Choose the desired A/P Account and Bank Account.
3. Mark a Bill (e.g. $100) and a Bill Credit (e.g. $50) for partial application.
4. Click Save then hit Refresh until the transaction is processed.

Results:
1. "Negative Bill Payment is not allowed."
2. The Bill Credit is not applied to the Bill
3. A separate Bill Payment transaction is created for the full amount of the Bill.

This is usually triggered by the different addresses, address internal ID and vendors on the Bill and on the Bill Credit.

The system detects the differences, thus creating separate lines and payments.

To resolve:
1. Edit the Bill or Bill Credit to correct the Billing Address, or
2. Use the Pay Single Vendor page as this will automatically source the Default Billing Address of the Vendor, or
3. Open the Bill and hit Make Payment button to manually apply the Bill Credit, or
4. Mark the Use Bill-To Address From Vendor box right below the To Be Printed box before hitting Save on the Pay Bills page