For the export of goods or the supply of services made to EU businesses on or after 1 January 2021, you will not need to submit an EC Sales List (ESL). You will have until 21 January 2021 to submit ESLs for sales made before 1 January 2021. After this date, ESLs for GB traders will fail electronic filing with HMRC.
You’ll still need to submit ESLs if you sell goods from Northern Ireland (known as Northern Ireland protocol transactions) to EU VAT-registered customers. HMRC will recognise the branch number of '121' to determine that you are a Northern Ireland trader.
VAT Filer will continue to enable ESL filing.
HMRC guidance explains How to report your EU sales from 1 January 2021