You need it for sure. Example: I have my business in Germany. If I write an invoice to a german company I add 19% VAT. If I sell to a company inside the EU but

You need it for sure. Example: I have my business in Germany. If I write an invoice to a german company I add 19% VAT. If I sell to a company inside the EU but not in Germany I add 0%, since it's a reverse charge. That means that the company in the EU country directly pays the taxes to their country and I don't have to pay it to my country. This solves a lot of bureaucracy hassle. Exception is where I am selling to no business, but a private person within the EU, I will charge VAT there and pay it to my country which redirects it to the EU country (that's called MOSS).