During the first D5 summit in London on 9 and 10 December 2014, the 5 countries signed the D5 Charter. The 5 countries are South Korea, Estonia, New Zealand, Israel and the UK. The Charter includes:
principles of digital development that each government of the country commits to working towards,acknowledging that they will not be able to meet all of the criteria on joining
the ways that the 5 countries will work together to support each other and help each other to become better digital governments
how the D5 will meet each year
https://www.gov.uk/government/publications/d5-charter