Northern Ireland Protocol Bill

In respect of supermarket deliveries to Northern Ireland, it is really dead simple: those supermarkets sell only in Northern Ireland, so they would, of course, be appropriate for the green lane. But given the very large number of other businesses that send goods across to Northern Ireland, how do the Government propose to identify those businesses that are sending goods that are destined for the Republic and those that are sending them into Northern Ireland where they may be processed and then moved on to the Republic of Ireland? How will that work in practice?