Only a customer/vendor is allowed for document type &

What causes this issue?

This transaction contains the document type '&v1&' and several open
items. Document type '&v1&' has been so configured, however, that only
a customer or vendor is permitted.

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

System Response

Inconsistent transaction.

How to fix this error?

Go into the financial accounting configuration menu and change the
settings for document type '&v1&'. If the settings are correct, you must
check the calling transaction. To do this, contact your SAP consultant
or SAP directly.

Error message extract from SAP system. Copyright SAP SE.