Messages occurred during the document check (see the long text)

What causes this issue?

The document check produced warnings and/or errors. You can look at the
details in the menu under Posting -> Display messages.

System Response

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

How to fix this error?

Procedure for System Administrators

Error message extract from SAP system. Copyright SAP SE.