Anyone with experience in this ?

Am wanting to start paying comms to affiliates who bring new clients to my online service.

How do I do this ?

If the affiliate has bought in R1000 business and is due R150 comms, does he have to send me an invoice so that I can claim it as a 'cost of sales' expense ?

What about the VAT ? Is it applicable for affiliate comms ?
Do I take 14% off the comms and give it to SARS ?

All advice appreciated.