Electors who are eligible to vote at a particular election or referendum will receive a polling card shortly before polling day, telling them where to vote. There are special arrangements for people who cannot get to a polling station to apply for a proxy or postal vote. Further details can be found in the section on postal and proxy voting.

Brentwood is in the Parliamentary constituency of Brentwood & Ongar. MPs are elected for a period of up to five years but a general election can be called earlier.

At the last UK Parliamentary Election on 12th December 2019, Michael Alex Burghart was returned to Parliament for the Brentwood & Ongar Constituency.

The Boundary Commission for England undertook a consultation on its proposals for changes to the constituency boundaries and published the results in June 2021.