One councillor will be elected for Electoral Ward 14 following the resignation of Hugh Gaffney to concentrate on his work as an MP.
Voting will take place between 7am and 10pm.
To be able to vote in this by-election, eligible residents must be registered to vote by midnight on Tuesday, September 3.
Applications for new postal or postal proxy votes and amendments to, or cancellation of, existing postal or proxy votes must be with the Electoral Registration Office by 5pm on Wednesday, September 4.
Applications for new proxy votes must be received by 5pm on Wednesday, September 11.
Returning officer Des Murray said: “It is important that everyone who is eligible has the opportunity to vote in the by-election, so I would encourage residents in the Thorniewood ward to make sure they are registered to vote.”
If you are not sure if you are registered to vote call the Electoral Registration Office on 0800 030 4333 or email [email protected]