Elections are taking place for the Scottish and Welsh Parliaments and some local councils and mayors in England on Thursday 7 May.

The BBC results service covers the Scottish and Welsh Parliament elections and council and mayoral elections in England.

There may also be community, parish or town council elections, council by-elections or local referenda where you are. Results for these elections are not covered by the BBC. They can be found on your local council website, alongside more detailed ward-level results.

The BBC gathers full election results directly from election counts in Scotland and Wales. For council and mayoral elections it uses results data from the Press Association (PA) alongside ward-level data it sources itself.

There are 129 members of the Scottish Parliament and they are all being elected on 7 May.

Seventy-three MSPs represent constituencies. The other 56 MSPs are elected to represent eight regions, with 7 MSPs each.

The boundaries for more than half of the constituencies and regions have been redrawn for this election and in some cases they have been given new names. The boundaries were redrawn to reflect changes in the population.

The Scottish Parliament elections use the additional member system. This means each voter can cast two votes.

In the 73 constituencies, people can vote for one candidate and the person with the most votes wins. This is called the first-past-the-post system.

In the eight regions, people vote for a party or an independent candidate. Each of the parties draw up lists of candidates they would like to see elected and they put them in order of preference.

The regional votes are used to work out the number of MSPs each party or independent candidate should have given the proportion of votes they received. This is then adjusted to take account of the number of constituency MSPs already elected for each party.

The party's list of candidates is used (in the same order of preference) to fill the regional seats until each party has the number of MSPs proportional to the votes they received.

Votes will be counted in Scotland during the day on Friday 8 May. Results are expected from the constituencies during the afternoon and the regions will come after that.

There are 129 seats in the Scottish Parliament. A party needs to win 65 seats to get an overall majority.

As the parliament is voted for, in part, using a form of proportional representation it can make majorities harder to achieve than under a first-past-the-post system such as the UK General Election.

In cases where no single party wins a majority, the parties with the most seats have a few options. They can hold power by trying to forge an alliance to create a power-sharing agreement or a coalition to form a majority administration. The SNP agreed a power-sharing agreement with the Scottish Greens in 2021.

Alternatively, a party with a large number of seats can aim to reach agreements with smaller parties to support it in the parliament in the event of a confidence motion aimed at bringing down the government.

Another possibility is for the largest party to form a minority government as the SNP did in 2007. In a case like this, limited or sometimes no agreements are made with other parties, and the largest party aims to get support for each individual bill on an ad-hoc basis.

Of course it is possible for lower-placed parties to form some sort of coalition with others to get to the required number of seats for a majority, which then forces the largest party into opposition.

If no party is prepared to go down one of these paths, it could ultimately lead to fresh elections.

The change in the share of the vote for each party is calculated by comparing this election result with the result of the last election. In the case of Scotland the last election was fought on different boundaries.

In a case like this, the BBC uses "notional results" to project what the previous results would have been if the new boundaries had been in place at the last election.

When the boundaries and electoral system change, it is important to have an idea of how many votes each party would have had if the new boundaries had been in place last time the seats were contested.

This way, the change in the share of the vote for each party can be calculated on a like-for-like basis.

This is not an exact science. When boundaries are redrawn and a place is moved into a new electoral area there is no official record of how people in that place voted.

This is where the experience and expertise of analysts comes in.

To calculate the notional results, analysts use maps of the old and new boundaries and how people voted in the 2021 election. They look at the area and use demographic data to help them work out how people are likely to have voted.

Using this information, they recalculate the results of the last election to estimate the share of the vote each party would have had if the new boundaries had been in place.

It is this figure that is used by the BBC to calculate change in these areas.

This exercise is only carried out for the top five parties who stood in the constituencies at the last election: SNP, Conservative, Labour, Liberal Democrat, Scottish Green Party. At a regional level Alba and Reform UK were also included. Change figures at a constituency or regional level will not be available for any party that stood in 2021 that is outside this group.

A new electoral system and new boundaries have been introduced for this election to the Welsh Parliament or Senedd.

The old system involving constituencies and regions has been replaced by 16 new constituencies. Voters get one vote and choose a party or independent candidate. A calculation is then made to elect six representatives for each constituency area. This means there are 96 Members of the Senedd (MS), up from 60 in 2021.

The Welsh Parliament is using a system of proportional representation called closed list proportional representation, which uses the D'Hondt formula to translate votes into seats.

In each constituency, voters choose one party or an independent candidate. Each of the parties draw up lists of candidates they would like to see elected and they put them in order of preference.

• In the first round of counting the party with the most votes wins a seat for the candidate at the top of its list
• In the second round, the winning party's vote is divided by two, and whichever party comes out on top in the re-ordered results wins a seat for their top candidate
• The process repeats itself, with the original vote of the winning party in each round being divided by one, plus their running total of MSs, until all six seats in the constituency have been taken.

Votes will be counted in Wales during the day on Friday 8 May and results are expected during the afternoon.

To win an election outright, one party would need to win enough seats in the Welsh Parliament to form a government on their own. To do that, one party would need to get one more seat than all the others added together but because the parliament is voted for using a form of proportional representation this is hard to do.

There are 96 seats in the Welsh Parliament. It is possible the largest party will fall short of getting the 49 seats needed to win outright.

In cases where no single party wins a majority, the largest party has a few options. It can hold power by trying to forge an alliance with a smaller party to create a power-sharing agreement or a coalition to form a majority administration.

Alternatively, it can aim to reach agreements with smaller parties to support the largest party in the parliament in the event of a confidence motion aimed at bringing down the government.

Another possibility is for the biggest party to form a minority government with limited or no agreements with other parties, and just try to get support in favour of each individual bill on an ad-hoc basis.

Of course it is possible for lower placed parties to form some sort of coalition together if they can form a majority, forcing the largest party into opposition.

If no party is prepared to go down one of these paths, it could ultimately lead to fresh elections.

The change in the share of the vote for each party is calculated by comparing this election result with the result at the last election. In the case of Wales the last election was fought on different boundaries with a different electoral system.

In a case like this, the BBC uses "notional results" to project what the previous result would have been if the new boundaries and electoral system had been in place at the last election.

When the boundaries and electoral system change, it is important to have an idea of how many votes each party would have had if the new boundaries been in place last time the seats were contested.

This way, the change in the share of the vote for each party can be calculated on a like-for-like basis.

This is not an exact science. When boundaries are redrawn and a place is moved from one electoral area into another there is no official record of how the people in that place voted. This is where the experience and expertise of analysts comes in.

To calculate the notional results, analysts use maps of the old and new boundaries and how people voted in the 2021 election. They look at the area, and use local knowledge and professional judgement to help them work out how people are likely to have voted.

Using this information, they recalculate the results of the last election to estimate the share of the vote each party would have had if the new boundaries had been in place.

It is this figure that is used by the BBC to calculate change in these areas.

This exercise is only done for the larger parties at the last election: Labour, Conservative, Plaid Cymru, Liberal Democrat, Abolish the Welsh Assembly, Green, Reform UK, UKIP and Independents. Change figures at a constituency level will not be available for any party outside this group that stood in 2021.

There are elections to 136 councils in England. Six county councils, 48 district councils, 32 London boroughs, 32 Metropolitan councils and 18 unitary authorities including two new unitaries of West Surrey and East Surrey. There are also elections for six city mayors; five in London and one in Watford.

Counting is taking place at different times in different places. Forty-six councils are expected to declare their results in the early hours of Friday 8 May. A further 85 will count votes during the day on Friday and the final five are expected to declare their results on Saturday. Results for the mayoral contests are all expected during the afternoon on Friday.

Council and mayoral elections use the first-past-the-post voting system. The public gets to vote for one candidate and the person with the most votes wins. In council wards or divisions where more than one seat is up for election the electorate can vote for one candidate per seat. In these cases parties will often stand more than one candidate. All the votes in the ward are counted together and the seats are allocated to the candidates who have received the most votes.

If a party has more than half of the councillors on a council, it is deemed to be 'in control' of that council. If no party has more than half of the council seats, the council is described as having 'no party majority' or 'hung'.

If a party did not have enough seats to control a council before the election but goes on to win more than half the seats on 7 May, this is described as a 'gain'.

This may be a gain from another party, or it may be that before the election no party had enough seats to control the council. In this case it is a gain from no party majority.

If the party already controlled the council before the election and they hold more than half the seats again after this election this is described as a 'hold'.

Council control prior to the election is defined by the BBC, the Press Association and others as the party, if any, that had a majority in the days running up to the poll.

This may be different to the party that won a majority of seats at the last election.

For example, a party may have won control of a council at the last election but then have lost their majority in the meantime through defections or by-elections.

If that party were to win the council again this year, the BBC would describe this as a gain for that party rather than a hold.

The change in the number of councillors for each party is calculated by comparing this election result with the result the last time these seats were contested, which for the majority of these councils was 2022.

There are some areas where change is more difficult to calculate because there are boundary changes which may also change the number of councillors representing each ward.

In cases like this, the BBC uses "notional results" to project what the previous result would have been if the new boundaries had been in place at the last election.

When the boundaries of council wards change, it is important to have an idea of how many councillors each party would have had if the new boundaries been in place last time the seats were contested.

This way, the change in the number of councillors elected for each party can be calculated on a like-for-like basis.

This is not an exact science. When boundaries are redrawn and an area is moved from one council ward into another there is no official record of how that area voted.

This is where the experience and expertise of analysts comes in.

To calculate the notional results, analysts use maps of the old and new boundaries. They look at the area, and use local knowledge and professional judgement to help them work out how people are likely to have voted.

Using this information, they recalculate the results of the last election to show how many councillors each party would have had if the new boundaries had been in place.

It is this figure that is used by the BBC to calculate change in these areas.

You can see if an area has had boundary changes in the 'About this council' section at the bottom of each council results page.

Banners appear at the top of the front page of the BBC News website, live pages and stories related to the election.

Scorecards appear in election live pages, in stories about the election and on social media.

They are ordered by the number of council or devolved parliament seats a party has won. This will change during the counting period as results come in.

When two parties are tied, the order is determined the number of votes they have won.

For most councils, elections for these seats were last held in 2022, and so we compare new results to this baseline year to show change figures for the parties.

For the Scottish and Welsh Parliaments change is against the notional results for the 2021 elections.

Vacant council seats are those which are left unfilled after this set of elections because a candidate in the electoral division or ward died after the close of nominations.

In these cases nominations are re-opened and a new election is held within 35 working days.