According to input from the MHRA, batches needed to be released into the market prior to 31st December 2020 in order to be considered a legacy pack. Anything after that is determined as a future GB pack for that market.
With respect to packs exported from the European Union (EU) to any third country (e.g. United Kingdom), the European has amended Article 22 of Commission Delegated Regulation (EU) 2016/161. As a result, it is no longer be required to decommission packs - in accordance with Article 22 - when such packs are exported from the EU to Great Britain.
However, the import of such non-decommissioned packs to the EU (via Ireland, Malta, Cyprus and the United Kingdom with respect to Northern Ireland) will be possible provided that:
the wholesale distributor or the marketing authorisation holder established in the
EU and responsible for the export of the medicinal product to the United Kingdom
has verified the pack against the EMVS;
the wholesale distributor importing the product into Northern Ireland, Ireland,
Cyprus or Malta has verified the pack against the EMVS.
For more information, please see the European Commission’s Notice C (2020) 9264 on the Application of the Union’s pharmaceutical acquis in markets historically dependent on medicines supply from or through Great Britain after the end of the transition period published on 22nd December 2020.