As part of a status review you need to establish the nature of the worker’s job and whether other workers who are employees are doing similar work under similar terms and conditions. You certainly need to examine closely the period up to the take-on date if the worker
Question the engager to find out why there was a change in the taxation/NICs treatment. Ask who suggested the change and why. Check whether or not the office dealing with the engager’s employees was consulted. Ask the engager whether the worker works alongside employees doing similar duties.