UPDATE (24th Jan) : UK Policy is NOT to implement beyond the Implementation period completion day
Exit day is 31st January (end of this month)
Implementation period completion day is 31st December (this is the end of the transition period)
The Withdrawal Agreement agreed between the UK and the EU in November 2019 will be ratified in the UK and the EU imminently. This will bring about an ordered UK exit from the EU, and initiate a Transition Period.
The Transition Period will operate for 2020. During the Transition Period EU law enacted and in force by 31st December 2020 will be implemented in the UK, even if it has implementation deadlines after 31st December.
UPDATE (24th Jan) : For our purposes, this means the 2018 EU Circular Waste Economy Package will be implemented in the UK. The 2019 EU Single-Use Plastics Directive would not be implemented.
In addition, EU laws already implemented in the UK but with long tail deadlines for e.g. product bans (e.g. menthol cigarettes) that apply after Exit day or after Implementation period completion day, will still apply in the UK.
The envisaged purpose of the Transition Period is for the UK and the EU to agree alternative arrangements for trade in goods, primarily, that will subsist from 1st January 2021.
For our purposes, this means the new UK chemicals regime, the new UK medicines regime, the new UK equipment label (UKCA Mark), and UK issued certificates of all kinds, will need to be in place by end of 2020. Expect unilateral arrangements for EU goods and chemicals etc circulation in the UK for a limited period after 31st December 2020. I Blog posted a few days ago about hops and the later date available for circulation of EU hops in the UK.
There could also be unilateral arrangements on the EU side for limited time-length goods circulation in the EU.
A key issue is acceptance on both sides of certificates issued, and the matter of double testing for chemicals, medicines etc.