The EU UK Trade Agreement establishes zero tariffs or quotas on trade between the UK and the EU, where goods meet the relevant rules of origin. To benefit from free trade, goods will have to be of UK or EU origin. This means they must meet the UK-EU preferential rules of origin based on where the products or ingredients used in their production come from.
Goods that do not meet the rules of origin can still be traded but they will not be able to benefit from preference under the TCA and may have to pay the standard (“Most Favoured Nation”) tariffs that the EU and UK apply to imports
Read more at - https://www.gov.uk/government/publications/rules-of-origin-for-goods-moving-between-the-uk-and-eu-from-1-january-2021