On February 2nd, 2019, the Department for Business, Energy & Industrial Strategy of the government of the UK published the UKCA guidance in this regard.
According to this official publication, this label should replace the CE logo on your products to be placed into the UK’s market, under certain conditions:
UKCA stands for UK Conformity Assessed.
Without a Brexit deal with the European Union and if approved by the UK Parliament, the UKCA marking should apply to products that require 3rd party assessment of conformity.
Fortunately, the assessment rules should remain similar to the CE marking ones.
Furthermore, CE marking should still be authorized in the UK for self-declarations of conformity, such as the obligation of RoHS DoC under the CE marking.