In the unlikely event that the UK leaves the EU with a No Deal, a document 'How to prepare if the UK leaves the EU with no deal' has been prepared:
https://www.gov.uk/government/collections/how-to-prepare-if-the-uk-leaves-the-eu-with-no-deal?utm_source=4bdca462-4e79-46dd-80af-901bebfbc953&utm_medium=email&utm_campaign=govuk-notifications&utm_content=immediate