Most of Estonia's government services have been made available as an E-service to their citizens apart from the private sector. In Estonia citizens only have to use one form of ID which has an encrypted chip embedded in the card.
They even offer E-citizenship to foreigners. This allows persons to apply for E-citizenship remotely and register a business in Estonia. One can pay taxes and do pretty much everything online.
They were able to do this by implementing X-road which is a data exchange layer that allows multiple organizations and countries to integrate their data well.