Council staff are beginning house-to-house visits in an effort to increase the numbers of people completing their annual canvass form.
It is a legal requirement for electors to register each year and, so far, more than 55 per cent of households have returned the canvass forms delivered to every household during May.
Now canvas staff will be calling on homes which have not yet returned a form to encourage more to do so.
Councillor David Harrington, Stockton Council's Cabinet Member for Corporate Management and Finance, said: "With the elections for Police and Crime Commissioner taking place in the autumn, it is important that everyone updates their details on the form. If you are not registered as an elector, you can't vote in the elections.
"Perhaps what many people don't know is that credit agencies use the Electoral Register when assessing credit."
Residents are required to return a canvass form every year, whether or not there are any changes. If there are no changes, you can do this by using the website at www.stockton.gov.uk/annualcanvass
Changes to the electoral roll can be made up to 8 October.
For more information call the Electoral Helpline on (01642) 526196.