Commission % and VAT question

Morning everyone!

I work on private health, commission based (11%) on every patient/treatment I do.

I am self employed and I haven’t reach the £ amount to be VAT registered, so my boss is saying if I can’t add VAT to my monthly invoice, he will then take 20% of the total amount I made in commission each month as he doesn’t need to pay VAT twice.

When the company does VAT returns he will claim everything legally possible to claim… I only take 11% of the total price of treatments.

Can he deduct 20% from my final invoice but then claim VAT in those services I had provide every quarter when doing his vat returns?

To me it seems he will be claiming twice the VAT. Taking from my salary and claiming back when VAT returns are done.

Example: a patient will pay £210 for a treatment, I will get £23.10 from this service, they do charge VAT to the patient (175+VAT = £210), he will then claim VAT on the products the company buys for us to be able to do the treatment, machinery etc etc… but now he wants to take 20% from my commission as I can’t reflect VAT in my invoice.

I just need some advise before I go into a meeting so I can defend myself

Thanks in advance