You do not need to register if the sale to other EU countries is less than 10k. This coming from our accountant. We are launching this month and he has advised us to hold off, if it looks like we will reach the threshold then we can register. It's a lot of return to each individual country, so why stress when it's not necessary. I recommend talking to your accountant about this though, as he/she will be able to advise better based on your company information.