If you supply goods or services to customers in other EU countries, registering for VAT is not always needed. Deliveries to VAT-registered businesses within the EU are usually zero-rated, provided you have a valid customer VAT number and proof of the delivery. For sales to consumers, threshold amounts for each country may apply - once you exceed the threshold, you may have to register for VAT in that country and use local VAT rates.
Also, providing services involving real estate or carrying out assembly/installation services may require VAT registration abroad. In addition, special arrangements such as the One Stop Shop (OSS) may apply, which allows you to file VAT returns for cross-border e-commerce through a single portal.