Nine million people are being warned they have to take action in the next 24 hours or they will miss out on a chance to vote in the elections on May 6.
There are 145 local council elections, 13 mayoral votes and one by-election taking place on the same day.
There are elections for the Senedd Cymru in Wales and the Scottish Parliament as well as elections for Police and Crime Commissioners.
The deadline to register to vote is midnight on Monday, April 19, by 17% of people have not yet done it.
Craig Westwood, the Electoral Commission's director of policy, said: "It only takes five minutes - the time it takes to boil a kettle." reports The Mirror.
In England, you can register to vote through the government website here.
Outside of England details are available on the Electoral Commission site here.
You’ll need your National Insurance number, name and address details.
