What is the ruling on issuing a single invoice for two vehicles, one of which you are not selling, in order to facilitate obtaining what is most likely usurious bank financing, and must one leave this job immediately?

The questioner's action of issuing a single invoice for both the truck and the trailer involves two prohibitions: the first is forgery and misrepresentation of reality, and the second is aiding in sin if it is known that the one requesting the invoice will submit it to obtain an usurious loan. He is not required to leave his job, but he must repent to Allah Almighty for the aforementioned action and resolve not to return to similar acts.