If you were not able to determine the nature of the relationship between the payer and the worker with the first three factors, you have to pursue the analysis. The final factor, ‘integration’, should settle the question.
Integration has to be considered from the point of view of the worker, not the payer.
Where the worker integrates the payer’s activities to his own commercial activities, a business relationship probably exists. The worker is acting on his own behalf, he is not dependent on the payer’s business and he is in business for himself.