Individual voter registration: 5.5m yet to be transferred, Electoral Commission says
Some 5.5 million potential voters in England and Wales have yet to be transferred onto a new version of the electoral register, officials say.
People must now register to vote individually rather than - as in the past - being listed on a form filled in by one member of a household.
The Electoral Commission said 87% of electors had transferred automatically.
However, it said nobody would be unable to vote in the 2015 general election because of the changes.
That is because under transitional arrangements, nobody will be removed from the existing registers until they are closed, either in December 2015 or December 2016.
The commission said people living in rented accommodation, young people and students were among the most likely not to have been transferred, because their electoral register details did not match Department for Work and Pensions records.
People who have automatically transferred should have received a letter informing them of the change and there was a two-month advertising campaign to highlight the switch.
As well as the move to individual registration, people can also register to vote online under the new regime.
Electoral Commission chairwoman Jenny Watson said: "This has been a huge step forward, giving people a quick, easy and convenient option."
She said the number of people who transferred automatically was "encouraging", but added there was more work to be done to reach the other 5.5 million.
The transition to individual voter registration began in Scotland last month, and the system is already in place in Northern Ireland.