I'm a freelance in France so as a very small business I don't pay the VAT (Article 293 B of french tax law). If you check the price you will see that there is no VAT or tax included in it. That's why I don't have any tax ID or VAT number.
You can find your invoice in your JPresta account in the "Order history and details" menu.
If you don't see it make sure you registered an address in your account so the invoice can be generated.