Business Central (and previous versions of NAV) have a Service Connection that allows the use of the VIES service to look up/check the validity of VAT registration numbers of VAT registered businesses in the EU. This is the "EU VAT Reg. No. Validation Service Setup" service connection. As the UK is unfortunately leaving the EU on the 1st Jan 2021 this single service will not be able to be used to check the VAT reg numbers of UK businesses. HMRC has just released its alternative service called "Check a UK VAT number" the url is https://www.tax.service.gov.uk/check-vat-number/enter-vat-details and they have a developer hub that will grant software developers access to an API for it. What we in the UK will need is for both to work, so we need to keep the original VIES service connection so we can check EU businesses but will also need a new service connection to allow the system to check the validity of the UK vat reg number. Any EU traders will likewise also need this for checking UK numbers.
You will probably need to make it reference the country region code to determine which service connection to use.