A new regulation is published that allows requesting EU type-approvals for vehicles such as tractors and components such as engines that have an UK-issued type-approval. After the UK leaves the EU it is not possible anymore to place on the market vehicles and components with an EU type-approval issued by an UK authority since the UK won’t be an EU Member State anymore. This was already explained in a notice published by the European Commission early 2018 that can be found here.
Therefore, all vehicles and components with an UK type-approval or vehicles where components with an UK type-approval installed need to obtain a type-approval from an EU Member States (an EU27 type-approval). In the existing legislation this wasn’t allowed as only one EU type-approval per vehicle could be requested. However, the newly published Regulation 2019/26 changes this. Regulation 2019/26 makes it possible to obtain EU27 type-approvals for vehicles and components that currently have a type-approval issued by an UK authority.
You can find the legislation here.
The exact actions that need to be taken depends on the final Brexit arrangement. At the moment of writing this article it is still not clear if there will be a hard-Brexit, no-Brexit or Brexit with a deal.