To ensure that the correct customs classification is applied, companies can apply to customs for Binding Tariff Information which is valid throughout the EU for 3 years. HMRC has published a guide outlining the implications of BREXIT on this subject, including :
The UK equivalent of the European Binding Tariff Information (BTI) will be an Advance Tariff Ruling (ATR). ATRs will not be recognised by the European Union;
Existing BTIs will be converted into ATRs at 23:00 GMT on 31 December 2020, unless companies object.
Until 31 December 2020, applications must be made through the current system. Decisions issued before 1 January will be BTI which will then be converted into ATR, and decisions issued from 1 January 2021 onwards will automatically be ATR.
From 1 January 2021, companies wishing to obtain an ATR will first need to have an EORI GB number and intend to import/export to Great Britain.
Source: HRMC