As far as here in austria it's like this:
When you're below a certain value of money income (around EUR 4300,-- profit) with your bussiness (Kleinunternehmer) you don't need a VAT - theirfor you're not allowed to do the "deduction of input tax" (Vorsteuerabzug) and have to pay the tax as normal end users. Also you are not allowed to show VAT explicitly on your written bills.
When you're above this certain value or opt-in you'll get a VAT Nr. so you'll have to show the VAT amount on your bills - but theirfor you can buy things from other countries without paying tax.