So, my questions are... Based on what I have outlined above, do you think I am fine to pay models as I currently am, without the need for any invoices, or treating them as employees? They themselves are free to do work on other websites, and independently, and many of them do. They are not exclusively working with me.
You will never find an easy answer to this question, this a very grey area and therefore you would need specific advise in this regard to protect you and even then you could easily end up in a tribunal which decides the answer on a balance of probabilities (51% needed) if hmrc disagreed with your view. I would say at face value you possibly are very close to going over the line but equally there are many similar business types to yours that do not employee their "workers" there will never be any clarity here unless hmrc makes their rules clearer.
As a starting point hmrc provide the ability to do an employment status check to give an indictive answer, if this comes out ok ensure you print out details and repeat test ofetn (at least once a year)
You would probably be best served by using one of the specialists in this field such as qdos (qdoscontractor.com) to help with regard to drawing up contracts and providing ongoing specific support.
Presuming they are self employed you should never pay anyone with a proper invoice , the invoice should clearly show their main details including home address and i would recommend they also supply their UTR to prove that they are registered with hmrc.
Am I right in thinking that as long as the total money paid to me from the cam website stays under £85,000 each year, I do not have to worry about becoming VAT registered?
No - i am not 100% sure about the reverse charge treatment of cam modelling services but you would want to be careful about engaging eu based self employed individuals as the default treatment for business to business services is reverse charge in which case the payments you make to eu based models could be classed as your turnover for vat regitration purposes - note i am not saying this is the case it just is a deffo possibility that it could be.
On a similar them if you pay out money to non uk based companies providing services - eg facebook and google ads ! then in the same manner these payments are subject to reverse charge and will definately need to be added to your sales calculations for
What to include
To check if you’ve gone over the threshold in any 12-month period, add together the total value of your UK sales that are not VAT exempt, including:
services you received from businesses in other countries that you had to ‘reverse charge’