Letters are being sent out to voters ahead of the nationwide change in the way people register to vote.
From now on, voters will have to register individually, whereas previously the 'head of household' could register everyone at their address.
Around 80 per cent of voters in Hertsmere will have their records transferred without needing to take any action, but new applicants will need to sign up to the electoral register before December 2015.
Hertsmere Borough Council has begun writing to everyone in the borough who is registered to vote under the old 'household' system, explaining whether or not they will need to re-register.
Hertsmere Borough Council chief executive Donald Graham said: "It's really important that you look out for your letter and respond if it asks you to take action. You need to register in order to be able to vote. If you aren't registered to vote, you won't have the chance to have a say on who represents you."