In principle nothing . Except the last time the government proposed them , it was a onecardtorulethemall , tying together basically all government services DVLA , NHS , Criminal Records , National Insurance , etc . There are good reasons why you might want to silo off data namely that if someone compromises one database , they don ' t also get access to masses of other unrelated data . It basically would have provided a singlepointoffailure and been a goldmine for identity fraud if it were ever breached . Now , if it were merely ID cards like they have in some European countries which are literally just a form of ID like a passport and indeed can be used as such for flights inside the EU , then fine . But what ' s the point when most people already have a driving licence or passport ? For 99 % of people , an ID card would provide no useful functionality . Also , the last time the UK had statemandated ID was WW 2 when the threat of espionage or foreign saboteurs was considered serious and it was law to be able to provide official ID on demand . Having managed quite well since the 50 s without it , there was a natural resistance due to the negative associations that it was only something we ever needed during wartime when we were under siege .