UKCA (UK's suitability approval) marks, is the marking of new British products to be used, subject to parliamentary approval, for certain items placed on the UK market if the UK leaves the UE without a Brexit agreement.
If the UK leaves the European Union without an agreement you will be silent, in most cases, it can use the CE sign to show compliance with legal requirements and to sell products on the UK market after March 29, 2019. However, in some cases, you have to apply the sign New UKCA for products sold in the UK. You can check out this source:what is ukca certification & its marking process? & Blue Dice Solutions before you buy any kind of product.
When to use the UKCA marker
Mostly, but not all, the product currently covered by the CE sign will fall in the scope of the new UKCA sign. The rules around using the new UKCA marking will reflect those who currently apply to the application of CE.
In most cases, you can still use CE marks for products placed on the UK market. However, if your product requires an assessment of third-party conformity, and if this has been done by the English suit assessment body, you must apply a new UKCA sign after March 29, 2019 (if needed by the law). This won't happen if the conformity certificate has been transferred to the UE-recognized body (in this case the CE marking will apply).
Put a sign of UKCA
You must attach a UKCA sign with the product itself, but in some circumstances, it can be placed on packaging, in the manual, or in other supporting literature. Rules that include the use of UKCA signs vary depending on the specific laws that apply to the product.