Can I already invoice if my vAT number is still pending?

I've often heard that you can make purchases before you receive your vAT number, so that shouldn't be a problem. But invoicing before you have your vAT number... I would be careful with that :) It usually doesn't take very long, does it? So if you can wait a few more days, I would wait for your vAT number.

But I'm not an accountant, so I'm not 100% sure.