I am a small business owner selling handmade products. I usually work on a 'sale or return' basis with local stockists but I have just received my first purchase order from a stockist who is buying my products wholesale. Within the purchase order sent to me, they have included VAT, which I have never mentioned before in our discussions of purchase. I am registered as a business but am not VAT registered. Do I include this VAT in my invoice to them? Or is it unnecessary?