United Kingdom

UK legislation does not require the use of customs brokers. UK legislation does not define "customs brokers" and only defines "customs agents" as well as setting out relevant requirements for their use in section 21 of the Taxation (Cross Border) Trade Act 2018. Guidance on the use of customs agents can be found here -

https://www.gov.uk/guidance/appoint-someone-to-deal-with-customs-on-your-behalf