A normal election or civic cycle for a local authority is a term of 4 years. At the end of each cycle or term, often all, but sometimes a proportion of a council’s total number of seats will be automatically vacated and put back up for election.
Where authorities run more than one cycle, each respective term will last for 4 years. This means that the overall balance of power could effectively be changed each and every time that one of the cycles ends and the seats are put back up for a vote.
As a councillor elected at the beginning of an election cycle, your term before having to seek re-election or step down would normally be 4 years.
When an elected member or councillor decides to step down, leave or resign from their position or seat part way through the cycle, or is unable to continue for some other reason, a by election will be called just for that specific seat.
By elections can happen at any time throughout the election cycle.
The process is very much the same as a full council election in terms of the number of days between the election being called and run, and when nominations have to be in and all other administrative requirements have to be fulfilled.
However, a by election can and often is only run for a single Ward or Division, or for one of the seats within it if it has multiple seats.
It will be run to coincide with other elections if one is scheduled for a similar time, and the local Monitoring Officer does have some discretion over the dates of by elections, whereas scheduled local elections are normally held on the first Thursday in May.
With this level of flexibility, it might be the case that you know a by election is coming for a certain Ward or Division several months before. Alternatively, you could have very little notice at all.
Notices of By Elections are posted in the same way as normal Local Authority Elections, so you will leave yourself very little time to develop a campaign if you wait for the news to reach you in this way.
Local Media and the Council Minutes will be the most reliable sources of news for you to become aware of when a by election is due. But hearing by word of mouth from people involved with the council itself will always help you a lot more when information like this first becomes available.