Acting returning officer Ian Davidson said: “The electoral timetable is set out by law and so we are bound by these dates.
“If residents want to have their democratic say then they must be registered, so anyone who wants to vote in the upcoming by-election should make sure they can by registering in time.
“You can register to vote online, or you can contact our team who will be happy to help you.
“I would also encourage people to check now that they have valid ID to enable them to vote at a polling station; and if they do not, then to apply for the free alternative Voter Authority Certificate.
“We want to make sure that everyone is still able to cast their vote next month.”
Nominations will open on Monday for candidates with a deadline of next Friday 17 July, to apply.
Residents of the Essex constituency not already on the electoral register have until July 28 to apply for a vote.
