Acceptance document already exists for entry sheet

What causes this issue?

You are attempting to accept an entry sheet for which a (non-canceled)
acceptance document already exists. This situation should never arise
and is probably due to a program bug.

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?

Please inform your system administrator.

Procedure for System Administrators

Error message extract from SAP system. Copyright SAP SE.