HMRC has published information on Tariffs.
You can use this service to check the UK Global Tariff that will apply to goods imported post-Brexit. It also shows the difference between what you pay now and what you’ll pay from 1 January 2021.
The UK Global Tariff will apply to all goods imported from 1 January 2021 – which will include bringing in goods from EU Member States. (currently acquisitions, not imports).