Ltd Company client working for chiropractic practice, not employed

I have a Ltd Company client who is a chirpractor and provides his chiropractic services through his Ltd Company.

The chirpractic business owner operates a building and a shared reception and for the provision of those services my client pays 40% of his patient fee income to the business owner.

In this case, the business owner wants my client to invoice him for the fee income net of 40% charges rather than just collecting his takings abnd then paying the business owner the 40% charges separately.

My concern is that this looks more like an IR35 employee situation this way and might be more susceptable to a challenge.

Amy views?