Acct & may only be posted to internally for cash discount clearing

What causes this issue?

The attribute <ZH>Only automatic postings</> is not set in the cash
discount clearing account master record.
The posting to the cash discount clearing account is created
automatically if a vendor invoice is posted with cash discount
according to the net procedure. During clearing of the invoice, an
offsetting entry of the same amount is created which is cleared with
the original posting.
If manual postings to the cash discount clearing account were
permitted, then open items of this account could also be cleared
manually. This would lead to errors when clearing the accompanying
invoice.

System Response

The system refuses to post the invoice.

How to fix this error?

Make sure that the attribute <ZH>Only automatic postings</> is set in
the master record of the account named.

Error message extract from SAP system. Copyright SAP SE.