If you don’t have any acceptable form of photo ID
If you don’t already have an accepted form of photo ID, or you’re not sure whether your photo ID still looks like you, you can apply for a free voter ID document, known as a Voter Authority Certificate. You need to be registered to vote before you apply for a Voter Authority Certificate.
When you register to vote, you’ll be asked whether you have photo ID or if you want to apply for a Voter Authority Certificate, which is a separate process .
Apply for a free Voter Authority Certificate on the GOV.uk site
More information on the requirements for voter ID can be found on the Electoral Commission website.