The UK Government has provided some flexibility to UK traders that EU traders should be aware of: up until 31 December 2021, authorised UK importers have the possibility to defer their import formalities for up to 175 days from the date of entry of non-controlled EU goods into the UK. This means that UK importers will be authorised to enter the goods in their records at the time of import and provide full supplementary declarations to HMRC only up to 175 days afterward. To make the supplementary declaration, importers must be authorised to use simplified customs declarations processes, or ask an agent that is so authorised to help them. HMRC can issue penalties for non-compliance should traders fail to meet the appropriate deadline for supplementary declarations.
As of 1 January 2022, UK importers will no longer be able to benefit from the delayed import declarations. Therefore, all import formalities will be due before or upon arrival of the goods at the points of entry into the UK. If pre-authorised, the importers may still benefit from simplified customs procedures with an obligation to complete its formalities within a month.
Source ec.europa.eu