All sites published after September 2018 should now be totally compliant, and older sites must have published accessibility statements with plans by September 2020. Government Digital Services provides detailed information on how these regulations affect organisations and what must be done to meet them.
Understanding accessibility
Accessibility means more than putting things online. It means making your content and design clear and simple enough so that most people can use it without needing to adapt it, while supporting those who do need to adapt things.