County councils are elected in full every four years, with the last election having been in 2017. County councils are the upper part of a two-tier system of local government, with the area each covers subdivided into district councils with different responsibilities. These are first-past-the-post elections with a mixture of single-member and multi-member electoral divisions. There were previously twenty-six county councils, but there will only be twenty-four by the time of the election. Buckinghamshire County Council was replaced with a unitary authority, Buckinghamshire Council, on 1 April 2020. Northamptonshire County Council "declared itself effectively bankrupt" in February 2018 and two new unitary authorities, North Northamptonshire and West Northamptonshire, are due to replace it on 1 April 2021. There are thirty-six metropolitan boroughs, which are single-tier local authorities. Thirty-three of them elect a third of their councillors every year for three years, with no election in each fourth year. These councils hold their elections on the same timetable, and were due to hold an election in 2020 but not in 2021. However, due to the coronavirus pandemic, the May 2020 elections were postponed to May 2021. The remaining three metropolitan boroughs elect their councillors in full every four years. Rotherham Metropolitan Borough Council was due to hold an election for all councillors in May 2020, but this was postponed to 2021. Doncaster Metropolitan Borough Council was due to elect their councillors in 2021. Birmingham City Council holds its elections on a four-year cycle from 2018, so is not due to hold an election until 2022. Due to boundary changes, Salford City Council is also to elect all of its councillors in 2021, before returning to the thirds schedule. The remaining thirty-two metropolitan borough councils that elect their councillors in thirds will do so as usual at this election. There were previously fifty-five unitary authorities, but three more are due to be created by the May elections. Buckinghamshire County Council was replaced with a unitary authority, Buckinghamshire Council, on 1 April 2020; the first election to the new unitary authority was scheduled for May 2020, but due to the coronavirus pandemic was rescheduled for May 2021. Subsequent elections are due to be held every four years from 2025. Northamptonshire County Council is due to be replaced with two unitary authorities, North Northamptonshire and West Northamptonshire on 1 April 2021.