Value of call documentation will be negative

What causes this issue?

You are entering a credit memo or a subsequent credit. This would result
in a negative value in the call documentation of the referenced
contract.

System Response

The system prevents posting of the document with an error message.

How to fix this error?

Check whether you want to enter an invoice or a credit memo/subsequent
credit.
Check whether the assignment of the contract is correct and change it if
necessary.


&SYSTEMADMINISTRATION&

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

Error message extract from SAP system. Copyright SAP SE.