Enter either clearing account or "variable clearing" indicator

What causes this issue?

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

System Response

How to fix this error?

EIther enter a clearing account or mark the checkbox called
<ZH>Variable clearing</>
If you choose variable clearing, information in the item is used when
paying.

Procedure for System Administrators

Error message extract from SAP system. Copyright SAP SE.