Deliveries of goods and services are made from 1/1/2021 to the United Kingdom are not considered intra-Community.
The United Kingdom left the European Union on 31/1/2020 on the basis of Withdrawal Agreement, which provides for a transitional period ending on 31/12/2020. Until that date, Union law on VAT applies in the United Kingdom, while from 1/1/2021 Union law for VAT ceases to apply in the United Kingdom.
Therefore, deliveries of goods and services are made from 1/1/2021 to the United Kingdom are not considered intra-Community, therefore the Summary VIES of January 2021 and later should not include the "GB" prefix and VAT registration numbers of United Kingdom.
However, under the Ireland / Northern Ireland Protocol - the law of Union on VAT on goods - continues to apply in the North Ireland after the transition period.
Hence the deliveries of goods (not services) to the North Ireland continues after 1/1/2021 to be considered as intra-Community transaction and must be stated in the VIES tables of January 2021 and later. The prefix to be used for numbers Northern Ireland VAT registration is “XI”.