Following the resignation of Councillor Joe Fahmy, a by-election will be held in Tudor Ward on October 10.
Residents are being urged to complete and return the annual canvass forms sent to them in August detailing the eligible voters in their household.
This is a survey carried out every year in order to make sure that the register of electors is kept up-to-date.
All new electors are being advised to register online before September 24 at gov.uk/register-to-vote so they can cast their vote on October 10.
Polling stations will be open from 7am to 10pm and the deadline for new applications to vote by post must be received by 5pm on September 25.
For those wishing to stand in the by-election, nomination papers are available from Watford Town Hall and must be completed and submitted to the Returning Officer by 4pm on the September 13 2019.
The names of all candidates standing will be published on September 16. Full details on the by-election can be found at watford.gov.uk/elections