Usually, companies register for VAT in the country of their choice due to exceeding the limit of transactions to that country.
Example: It is February 2021 and company X has exceeded the limit for sales to Germany on 15 December 2020. What should I do in this situation?
Answer: If company X has exceeded the limit on 15 December 2020, it should be filing returns in Germany from that date. You should register for VAT in Germany as soon as possible and file backdated returns for the months from December 2020 until the month in which the company obtains a DE VAT number. If the company obtains the number in April 2021, then it will be necessary to submit the retroactive declarations for 3 months: December 2020, January, February and March 2021.