With sipgate basic you can set up a billing address different to your account's 999 emergency address.
Business customers (small office / home office usage) can also provide an EU VAT ID here.
To change your sipgate basic account's UK 999 Emergency Address please see this article instead.
To change your billing address and VAT ID please login to your account and open the settings menu:
Under VAT-ID / Billing address you'll find a Change option:
Please enter your details into the text fields that open and confirm with the Change button:
Enter your VAT number preceded by the country code (e.g. GB123456789) and without spaces.
If your VAT number isn't accepted please select Alternative billing address and enter your registered VAT address as it listed on the central VIES VAT Database.
Your sipgate basic billing address does not have to be a UK address.