BTW (VAT) number on invoice

I need my BTW (VAT) number to be displayed on the invoice of my purchase but I don't see any option to place any remarks when ordering. I tried to make an account through the corporate program to see if I could enter it here but it won't let me as I'm using a Hotmail account for my business. I tried calling the support line but I'm not getting through nor are they calling back. Kind regards