Posting rule requires declarant code; enter code or change settings

What causes this issue?

When defining posting rules for customs duties or fees, you selected
posting to the vendor account of the declarant. However, you did not
enter the relevant declarant code.

System Response

The system cannot perform the posting.

How to fix this error?

Enter a declarant code or change your settings in the Customizing
activity <LS>Define Posting Rules for Customs Fees and Duties</>.

Procedure for System Administrators

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

Error message extract from SAP system. Copyright SAP SE.