The European Council has changed the UK withdrawal date to either 12 April or 22 May 2019. The final date will be decided in a further vote of the House of Commons on the draft Withdrawal Agreement that the European Council endorsed on 25 November 2018.
ECHA advises companies to continue preparations for the UK withdrawal without an agreement, and hence without a transition period.
For companies which are established in the UK, the EU chemicals legislation will no longer apply to you if your chemical substances, mixtures or articles, biocidal product or active substances are placed on the market inly in the UK. It also happens to the companies that export certain chemicals directly to non-EU/EEA countries from the UK. However, it is important to follow the UK legislation as they intend to make the EU legislation valid within the UK after the withdrawal.
For companies which are EU-27-based the interactions with UK-based business partners will be impacted by the UK withdrawal.
You may find more specific information on https://echa.europa.eu/es/uk-withdrawal-from-the-eu