Vote 2011: Details of elections taking place across UK
Millions of voters across the UK will go to the polls on 5 May in national and local elections as well as the referendum on the Westminster voting system. Here's a rundown:
Referendum on changing Westminster parliament voting system
In the first UK-wide referendum since 1975, voters will be asked whether they want to keep the current first-past-the-post system for electing MPs or switch to the Alternative Vote system.
To take part, people need to be 18 years of age or over on polling day. Citizens of the United Kingdom and the Irish Republic and qualifying nationals of Commonwealth countries are eligible to vote.
They also need to be registered to vote. In England, Wales and Northern Ireland the deadline for applying to register to vote is midnight 14 April and in Scotland by midnight on 15 April. To register for a postal vote, people across the UK must apply by 1700 BST on 14 April. People can apply by fax or e-mail although e-mail applications must comprise of a scanned image of the signed application form.
As with all elections taking place on 5 May, polling stations will be open between 0700 and 2200 BST.
But votes will not begin to be counted in the referendum until 1600 BST on 6 May.
Results will be announced on a region-by-region basis for the North East of England; North West of England; Yorkshire and the Humber; East Midlands; West Midlands; East of England; London; South East of England, South West of England; Scotland; Wales and Northern Ireland.
The final result will be announced by chief counting officer, Electoral Commission head Jenny Watson.
Scottish Parliament elections
Scottish voters will go to the polls for the first time since 2007, when the SNP emerged as the largest party and formed a minority government.
Like four years ago, 129 MSPs will be elected to Holyrood - 73 through the constituency-based first-past-the-post system and 56 through a separate party list system in eight electoral regions.
The shape of the parliamentary map is significantly different this time.
The boundaries of more than half of the constituencies have been re-drawn since 2007 and one in six voters are now in a different seat than they were last time around.
Council elections due this year have been deferred until 2012 to avoid the voter confusion experienced in 2007 and give local government elections more prominence.
National Assembly elections
This is the first poll since 2007, after which Labour formed a coalition with Plaid Cymru.
As in Scotland, voters will be required to fill in two separate ballot papers.
Forty Assembly Members (AMs) will be elected from single constituencies under first-past-the-post. The second ballot will be used to elect four AMs from each of five electoral regions under a party list.
There have been no major boundary changes since 2007.
The new Assembly will have direct law-making powers in 20 devolved areas, such as health and education, after voters backed the move in a referendum in March.
Local council elections are due to take place next year.
Voters will go to the polls to elect 108 members of the Stormont Assembly.
In 2007, the Democratic Unionists emerged as the largest party in the power-sharing body with eight more seats than Sinn Fein.
Local council elections
In addition, voters will go the polls to elect 582 councillors in the first local elections for six years.
The elections were due to take place in 2009 but were delayed by two years pending a restructuring of local government. But plans to cut the number of councils from 26 to 11 were cancelled last year.
Local council elections
Seats will be up for grabs in 279 local authorities across England.
Some 30 unitary authorities and 124 district authorities, including Blackpool, Leicester, Nottingham and York, will be electing all their members for the first time since 2007.
A third of seats are being contested in 36 metropolitan boroughs, including Birmingham, Liverpool, Leeds and Sheffield, 19 unitary authorities and 70 district councils.
There are no elections in London this year.
By-election and mayoral elections
A by-election is being held in the constituency of Leicester South after the Labour MP, Peter Soulsby, stood down to take part in the first-ever mayoral contest in the city.
Labour will defend a majority of 8,808 in what will be the third by-election of this Parliament.
As well as Leicester, polls will also be held to elect mayors in Middlesbrough, Mansfield, Bedford and Torbay.