After the end of the transition, the UK stands to lose the benefit of EU trade agreements unless it has negotiated additional roll over arrangements or entirely new FTAs to apply from 1 January 2021.
At the time of updating this Q&A (October 2020), the UK had negotiated a significant number of continuity trade agreements with territories including South Korea, Switzerland, Chile, South Africa and Norway. The UK has also reached a trade agreement with Japan which is understood to be similar to the recent EU-Japan deal. However that still leaves a number of territories where talks are ongoing, including Canada, Mexico, Turkey and Singapore. Even where agreements have been reached, it should also not be assumed that they will necessarily replicate the benefits of existing EU trade agreements in full (for example, in relation to Japan, it is not thought that the UK has succeeded in matching the EU's agreement in all respects, although there are a small number of areas where it claims to have improved upon it). Click here for more detail.
How big is the impact?
The impact of losing the benefit of these trade agreements needs to be kept in perspective. According to the UK Government, the relevant agreements benefit only about 10% of the UK's total trade (note that this figure does not include Japan, but the EU-Japan trade agreement has only recently come into force). That said, for individual businesses that have significant customers in territories where benefits will not be preserved, the lack of a "big picture" impact will not be much comfort.